diff --git a/CMakeLists.txt b/CMakeLists.txt
index e58036a5cad..834a732ef40 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -164,86 +164,126 @@ endif()
 add_subdirectory(third-party)
 
 if(NOT DEFINED FXDIV_SOURCE_DIR)
-  set(ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG
-      ${CMAKE_POSITION_INDEPENDENT_CODE}
+  include(GNUInstallDirs)
+  get_extra_cmake_args_for_external_project(FXDIV_EXTRA_CMAKE_ARGS)
+  set(FXDIV_SOURCE_DIR
+      "${CMAKE_CURRENT_LIST_DIR}/backends/xnnpack/third-party/FXdiv"
   )
-  set(FXDIV_SOURCE_DIR "backends/xnnpack/third-party/FXdiv")
-  add_subdirectory("${FXDIV_SOURCE_DIR}")
-  set(CMAKE_POSITION_INDEPENDENT_CODE
-      ${ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG}
+  set(FXDIV_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/fxdiv")
+  set(FXDIV_INSTALL_DIR "${FXDIV_BINARY_DIR}/install")
+  set(FXDIV_HEADER "${FXDIV_INSTALL_DIR}/${CMAKE_INSTALL_INCLUDEDIR}/fxdiv.h")
+  ExternalProject_Add(
+    fxdivExternalProject
+    SOURCE_DIR "${FXDIV_SOURCE_DIR}"
+    BINARY_DIR "${FXDIV_BINARY_DIR}"
+    INSTALL_DIR "${FXDIV_INSTALL_DIR}"
+    BUILD_BYPRODUCTS "${FXDIV_HEADER}"
+    CMAKE_ARGS "${FXDIV_EXTRA_CMAKE_ARGS}"
+               -D
+               CMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+               -D
+               FXDIV_BUILD_TESTS=OFF
+               -D
+               FXDIV_BUILD_BENCHMARKS=OFF
   )
+  add_library(fxdiv INTERFACE IMPORTED)
+  set_property(TARGET fxdiv PROPERTY IMPORTED_LOCATION "${FXDIV_HEADER}")
 endif()
 
 if(EXECUTORCH_BUILD_CPUINFO)
   # --- cpuinfo
-  set(ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG
-      ${CMAKE_POSITION_INDEPENDENT_CODE}
+  set(CPUINFO_SOURCE_DIR
+      "${CMAKE_CURRENT_LIST_DIR}/backends/xnnpack/third-party/cpuinfo"
   )
-  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-  set(CPUINFO_SOURCE_DIR "backends/xnnpack/third-party/cpuinfo")
-  set(CPUINFO_BUILD_TOOLS
-      OFF
-      CACHE BOOL ""
+  set(CPUINFO_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/cpuinfo")
+  set(CPUINFO_INSTALL_DIR "${CPUINFO_BINARY_DIR}/install")
+  set(CPUINFO_LIBRARY
+      "${CPUINFO_INSTALL_DIR}/${CMAKE_INSTALL_LIBDIR}/libcpuinfo.a"
   )
-  set(CPUINFO_BUILD_UNIT_TESTS
-      OFF
-      CACHE BOOL ""
-  )
-  set(CPUINFO_BUILD_MOCK_TESTS
-      OFF
-      CACHE BOOL ""
-  )
-  set(CPUINFO_BUILD_BENCHMARKS
-      OFF
-      CACHE BOOL ""
-  )
-  set(CPUINFO_LIBRARY_TYPE
-      "static"
-      CACHE STRING ""
-  )
-  set(CPUINFO_LOG_LEVEL
-      "error"
-      CACHE STRING ""
+
+  get_extra_cmake_args_for_external_project(CPUINFO_EXTRA_CMAKE_ARGS)
+  ExternalProject_Add(
+    cpuinfoExternalProject
+    SOURCE_DIR "${CPUINFO_SOURCE_DIR}"
+    BINARY_DIR "${CPUINFO_BINARY_DIR}"
+    INSTALL_DIR "${CPUINFO_INSTALL_DIR}"
+    BUILD_BYPRODUCTS "${CPUINFO_LIBRARY}"
+    CMAKE_ARGS "${CPUINFO_EXTRA_CMAKE_ARGS}"
+               -D
+               CMAKE_POSITION_INDEPENDENT_CODE=ON
+               -D
+               CPUINFO_BUILD_TOOLS=OFF
+               -D
+               CPUINFO_BUILD_UNIT_TESTS=OFF
+               -D
+               CPUINFO_BUILD_MOCK_TESTS=OFF
+               -D
+               CPUINFO_BUILD_BENCHMARKS=OFF
+               -D
+               CPUINFO_LIBRARY_TYPE=static
+               -D
+               CPUINFO_LOG_LEVEL=error
+               -D
+               CMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+               -D
+               CLOG_SOURCE_DIR="${CPUINFO_SOURCE_DIR}/deps/clog"
   )
-  set(CLOG_SOURCE_DIR "${CPUINFO_SOURCE_DIR}/deps/clog")
-  add_subdirectory("${CPUINFO_SOURCE_DIR}")
-  set(CMAKE_POSITION_INDEPENDENT_CODE
-      ${ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG}
+  add_library(cpuinfo STATIC IMPORTED)
+  set_property(TARGET cpuinfo PROPERTY IMPORTED_LOCATION "${CPUINFO_LIBRARY}")
+  add_dependencies(cpuinfo cpuinfoExternalProject)
+  # Trailing slash matters here! "Move everything from the temporary pthreadpool
+  # install directory to the proper install directory."
+  install(DIRECTORY "${CPUINFO_INSTALL_DIR}/"
+          DESTINATION "${CMAKE_INSTALL_PREFIX}"
   )
 endif()
 
 if(EXECUTORCH_BUILD_PTHREADPOOL)
   # --- pthreadpool
-  set(ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG
-      ${CMAKE_POSITION_INDEPENDENT_CODE}
-  )
-  set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-  set(PTHREADPOOL_SOURCE_DIR "backends/xnnpack/third-party/pthreadpool")
-  set(PTHREADPOOL_BUILD_TESTS
-      OFF
-      CACHE BOOL ""
+  set(PTHREADPOOL_SOURCE_DIR
+      "${CMAKE_CURRENT_LIST_DIR}/backends/xnnpack/third-party/pthreadpool"
   )
-  set(PTHREADPOOL_BUILD_BENCHMARKS
-      OFF
-      CACHE BOOL ""
-  )
-  set(PTHREADPOOL_LIBRARY_TYPE
-      "static"
-      CACHE STRING ""
-  )
-  set(PTHREADPOOL_ALLOW_DEPRECATED_API
-      ON
-      CACHE BOOL ""
+  include(GNUInstallDirs)
+  set(PTHREADPOOL_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/pthreadpool")
+  set(PTHREADPOOL_INSTALL_DIR "${PTHREADPOOL_BINARY_DIR}/install")
+  set(PTHREADPOOL_LIBRARY
+      "${PTHREADPOOL_INSTALL_DIR}/${CMAKE_INSTALL_LIBDIR}/libpthreadpool.a"
   )
+  get_extra_cmake_args_for_external_project(PTHREADPOOL_EXTRA_CMAKE_ARGS)
   if(APPLE)
-    set(PTHREADPOOL_SYNC_PRIMITIVE
-        "condvar"
-        CACHE STRING ""
+    list(APPEND PTHREADPOOL_EXTRA_CMAKE_ARGS -D
+         PTHREADPOOL_SYNC_PRIMITIVE=condvar
     )
   endif()
-  add_subdirectory("${PTHREADPOOL_SOURCE_DIR}")
-  set(CMAKE_POSITION_INDEPENDENT_CODE
-      ${ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG}
+  ExternalProject_Add(
+    pthreadpoolExternalProject
+    SOURCE_DIR "${PTHREADPOOL_SOURCE_DIR}"
+    BINARY_DIR "${PTHREADPOOL_BINARY_DIR}"
+    INSTALL_DIR "${PTHREADPOOL_INSTALL_DIR}"
+    BUILD_BYPRODUCTS "${PTHREADPOOL_LIBRARY}"
+    CMAKE_ARGS ${PTHREADPOOL_EXTRA_CMAKE_ARGS}
+               -D
+               PTHREADPOOL_BUILD_TESTS=OFF
+               -D
+               PTHREADPOOL_BUILD_BENCHMARKS=OFF
+               -D
+               PTHREADPOOL_LIBRARY_TYPE=static
+               -D
+               PTHREADPOOL_ALLOW_DEPRECATED_API=ON
+               -D
+               CMAKE_POSITION_INDEPENDENT_CODE=ON
+               -D
+               CMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+  )
+  add_library(pthreadpool STATIC IMPORTED)
+  set_property(
+    TARGET pthreadpool PROPERTY IMPORTED_LOCATION "${PTHREADPOOL_LIBRARY}"
+  )
+  add_dependencies(pthreadpool pthreadpoolExternalProject)
+  # Trailing slash matters here! "Move everything from the temporary pthreadpool
+  # install directory to the proper install directory."
+  install(DIRECTORY "${PTHREADPOOL_INSTALL_DIR}/"
+          DESTINATION "${CMAKE_INSTALL_PREFIX}"
   )
 endif()
 
@@ -731,7 +771,10 @@ if(EXECUTORCH_BUILD_EXECUTOR_RUNNER)
     endif()
 
     set(CMAKE_EXECUTABLE_SUFFIX ".html")
-    target_link_options(executor_runner PUBLIC -sALLOW_MEMORY_GROWTH --embed-file "${WASM_MODEL_DIR}@/")
+    target_link_options(
+      executor_runner PUBLIC -sALLOW_MEMORY_GROWTH --embed-file
+      "${WASM_MODEL_DIR}@/"
+    )
   endif()
 endif()
 
diff --git a/backends/xnnpack/CMakeLists.txt b/backends/xnnpack/CMakeLists.txt
index b6ba211ecb3..c4c5068d197 100644
--- a/backends/xnnpack/CMakeLists.txt
+++ b/backends/xnnpack/CMakeLists.txt
@@ -92,9 +92,8 @@ target_include_directories(
                            ${EXECUTORCH_ROOT}/third-party/flatbuffers/include
 )
 
-set(xnnpack_third_party pthreadpool extension_threadpool cpuinfo)
-
 include(cmake/Dependencies.cmake)
+set(xnnpack_third_party XNNPACK pthreadpool extension_threadpool cpuinfo)
 
 list(TRANSFORM _xnnpack_backend__srcs PREPEND "${EXECUTORCH_ROOT}/")
 add_library(xnnpack_backend ${_xnnpack_backend__srcs})
diff --git a/backends/xnnpack/cmake/Dependencies.cmake b/backends/xnnpack/cmake/Dependencies.cmake
index 71ade68ccb2..b6fd547e2bc 100644
--- a/backends/xnnpack/cmake/Dependencies.cmake
+++ b/backends/xnnpack/cmake/Dependencies.cmake
@@ -10,73 +10,83 @@ set(THIRD_PARTY_ROOT "${CMAKE_CURRENT_SOURCE_DIR}/third-party")
 
 # --- XNNPACK
 
-# Setting this global PIC flag for all XNNPACK targets. This is needed for
-# Object libraries within XNNPACK which must be PIC to successfully link this
-# static libXNNPACK
-set(ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG
-    ${CMAKE_POSITION_INDEPENDENT_CODE}
-)
-set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-
 set(XNNPACK_SOURCE_DIR "${THIRD_PARTY_ROOT}/XNNPACK")
 set(XNNPACK_INCLUDE_DIR "${XNNPACK_SOURCE_DIR}/include")
-set(XNNPACK_LIBRARY_TYPE
-    "static"
-    CACHE STRING ""
+
+include(ExternalProject)
+include(GNUInstallDirs) # For CMAKE_INSTALL_LIBDIR
+set(XNNPACK_INSTALL_DIR "${CMAKE_CURRENT_BINARY_DIR}/XNNPACK/install")
+set(XNNPACK_STATIC_LIB
+    "${XNNPACK_INSTALL_DIR}/${CMAKE_INSTALL_LIBDIR}/libXNNPACK.a"
 )
-set(XNNPACK_BUILD_BENCHMARKS
-    OFF
-    CACHE BOOL ""
+set(XNNPACK_MICROKERNELS_STATIC_LIB
+    "${XNNPACK_INSTALL_DIR}/${CMAKE_INSTALL_LIBDIR}/libxnnpack-microkernels-prod.a"
 )
-set(XNNPACK_BUILD_TESTS
-    OFF
-    CACHE BOOL ""
+get_extra_cmake_args_for_external_project(XNNPACK_EXTRA_CMAKE_ARGS)
+ExternalProject_Add(
+  XNNPACKExternalProject
+  SOURCE_DIR ${XNNPACK_SOURCE_DIR}
+  # Not 100% clear on these locations
+  BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/XNNPACK
+  INSTALL_DIR ${XNNPACK_INSTALL_DIR}
+  INSTALL_BYPRODUCTS ${XNNPACK_STATIC_LIB} ${XNNPACK_MICROKERNELS_STATIC_LIB}
+  CMAKE_ARGS
+    ${XNNPACK_EXTRA_CMAKE_ARGS}
+    -D
+    XNNPACK_LIBRARY_TYPE=static
+    -D
+    XNNPACK_BUILD_BENCHMARKS=OFF
+    -D
+    XNNPACK_BUILD_TESTS=OFF
+    -D
+    XNNPACK_ENABLE_AVXVNNI=OFF
+    # Work around observed failure:
+    # https://github.com/pytorch/executorch/pull/10362#issuecomment-2906391232
+    -D
+    XNNPACK_ENABLE_AVX512VNNIGFNI=OFF
+    -D
+    ENABLE_XNNPACK_WEIGHTS_CACHE=${EXECUTORCH_XNNPACK_ENABLE_WEIGHT_CACHE}
+    -D
+    ENABLE_XNNPACK_SHARED_WORKSPACE=${EXECUTORCH_XNNPACK_SHARED_WORKSPACE}
+    -D
+    XNNPACK_ENABLE_KLEIDIAI=${EXECUTORCH_XNNPACK_ENABLE_KLEIDIAI}
+    -D
+    CMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+    -D
+    XNNPACK_BUILD_ALL_MICROKERNELS=OFF
+    -D
+    CMAKE_POSITION_INDEPENDENT_CODE=ON
 )
-set(XNNPACK_ENABLE_AVXVNNI
-    OFF
-    CACHE BOOL ""
-  )
-# Work around observed failure: https://github.com/pytorch/executorch/pull/10362#issuecomment-2906391232
-set(XNNPACK_ENABLE_AVX512VNNIGFNI
-  OFF
-  CACHE BOOL "")
 
-if(EXECUTORCH_XNNPACK_ENABLE_KLEIDI)
-    set(XNNPACK_ENABLE_KLEIDIAI
-        ON
-        CACHE BOOL ""
-    )
-else()
-    set(XNNPACK_ENABLE_KLEIDIAI
-        OFF
-        CACHE BOOL ""
-    )
-endif()
+add_library(XNNPACK STATIC IMPORTED GLOBAL)
+# TODO: this probably doesn't work on Windows.
+set_property(TARGET XNNPACK PROPERTY IMPORTED_LOCATION ${XNNPACK_STATIC_LIB})
+
+add_dependencies(XNNPACK XNNPACKExternalProject)
 
+add_library(xnnpack-microkernels-prod STATIC IMPORTED GLOBAL)
+set_property(
+  TARGET xnnpack-microkernels-prod PROPERTY IMPORTED_LOCATION
+                                            ${XNNPACK_MICROKERNELS_STATIC_LIB}
+)
+add_dependencies(xnnpack-microkernels-prod XNNPACKExternalProject)
 
-set(XNNPACK_BUILD_ALL_MICROKERNELS
-    OFF
-    CACHE BOOL ""
+set_target_properties(
+  XNNPACK PROPERTIES INTERFACE_LINK_LIBRARIES xnnpack-microkernels-prod
 )
-add_subdirectory("${XNNPACK_SOURCE_DIR}")
-include_directories(SYSTEM ${XNNPACK_INCLUDE_DIR})
-list(APPEND xnnpack_third_party XNNPACK)
-install(TARGETS xnnpack-microkernels-prod
-    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
+install(DIRECTORY ${XNNPACK_INSTALL_DIR}/ DESTINATION ${CMAKE_INSTALL_PREFIX})
 
 if(EXECUTORCH_XNNPACK_ENABLE_KLEIDI)
-    if(TARGET kleidiai)
-        install(TARGETS kleidiai
-            LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-            ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-            PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-    endif()
+  add_library(kleidiai SHARED IMPORTED)
+  find_library(
+    KLEIDIAI_LIBRARY kleidiai
+    PATHS "${CMAKE_CURRENT_BINARY_DIR}/XNNPACK/kleidiai-source"
+  )
+  if(KLEIDIAI_LIBRARY)
+    message(WARNING "Can't find KleidiAI, skipping install")
+    install(FILES ${KLEIDIAI_LIBRARY} PUBLIC_HEADER
+            DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+  endif()
 endif()
-
-# Revert PIC Flag to what it originally was
-set(CMAKE_POSITION_INDEPENDENT_CODE
-    ${ORIGINAL_CMAKE_POSITION_INDEPENDENT_CODE_FLAG}
-)
diff --git a/devtools/bundled_program/CMakeLists.txt b/devtools/bundled_program/CMakeLists.txt
index ee7fb34e37f..b1b227b3528 100644
--- a/devtools/bundled_program/CMakeLists.txt
+++ b/devtools/bundled_program/CMakeLists.txt
@@ -4,18 +4,20 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
-set(
-  _schema_files
-  bundled_program_schema.fbs
-  scalar_type.fbs
-)
+set(_schema_files bundled_program_schema.fbs scalar_type.fbs)
 
 set(_schema_outputs)
 foreach(schema_file ${_schema_files})
-  list(APPEND _bundled_program_schema__srcs "${CMAKE_CURRENT_SOURCE_DIR}/schema/${schema_file}")
+  list(APPEND _bundled_program_schema__srcs
+       "${CMAKE_CURRENT_SOURCE_DIR}/schema/${schema_file}"
+  )
 
   string(REGEX REPLACE "[.]fbs$" "_generated.h" generated "${schema_file}")
-  list(APPEND _schema_outputs "${DEVTOOLS_INCLUDE_DIR}/executorch/devtools/bundled_program/schema/${generated}")
+  list(
+    APPEND
+    _schema_outputs
+    "${DEVTOOLS_INCLUDE_DIR}/executorch/devtools/bundled_program/schema/${generated}"
+  )
 endforeach()
 
 file(MAKE_DIRECTORY ${DEVTOOLS_INCLUDE_DIR}/executorch/devtools/bundled_program)
@@ -32,20 +34,13 @@ add_custom_command(
 )
 
 add_library(
-  bundled_program
-  ${_schema_outputs}
-  ${CMAKE_CURRENT_SOURCE_DIR}/bundled_program.cpp
-)
-target_link_libraries(
-  bundled_program
-  PUBLIC
-    executorch
+  bundled_program ${_schema_outputs}
+                  ${CMAKE_CURRENT_SOURCE_DIR}/bundled_program.cpp
 )
+target_link_libraries(bundled_program PUBLIC executorch)
 target_include_directories(
-  bundled_program
-  PUBLIC
-    ${DEVTOOLS_INCLUDE_DIR}
-    ${PROJECT_SOURCE_DIR}/third-party/flatbuffers/include
+  bundled_program PUBLIC ${DEVTOOLS_INCLUDE_DIR}
+                         ${PROJECT_SOURCE_DIR}/third-party/flatbuffers/include
 )
 
 install(
diff --git a/tools/cmake/Utils.cmake b/tools/cmake/Utils.cmake
index 732f5ddd1e7..941ec9a9954 100644
--- a/tools/cmake/Utils.cmake
+++ b/tools/cmake/Utils.cmake
@@ -278,3 +278,32 @@ macro(find_package_torch)
     find_package(Torch CONFIG REQUIRED)
   endif()
 endmacro()
+
+# In order to support cross compiling, we need to propagate a bunch of CMake
+# variables to ExternalProject. Call this to get the current values of all
+# relevant variables, which should then be passed to CMAKE_ARGS.
+function(get_extra_cmake_args_for_external_project outVar)
+  set(VARIABLES_TO_PROPAGATE
+      ANDROID_ABI
+      ANDROID_PLATFORM
+      CMAKE_ARCHIVE_OUTPUT_DIRECTORY
+      CMAKE_BUILD_TYPE
+      CMAKE_C_COMPILER_LAUNCHER
+      CMAKE_CXX_COMPILER_LAUNCHER
+      CMAKE_FIND_ROOT_PATH
+      CMAKE_OSX_DEPLOYMENT_TARGET
+      CMAKE_TOOLCHAIN_FILE
+      DEPLOYMENT_TARGET
+      PLATFORM
+  )
+  set(${outVar} "")
+  foreach(var ${VARIABLES_TO_PROPAGATE})
+    if(DEFINED ${var})
+      list(APPEND ${outVar} -D "${var}=${${var}}")
+    endif()
+  endforeach()
+  set(${outVar}
+      ${${outVar}}
+      PARENT_SCOPE
+  )
+endfunction()
diff --git a/tools/cmake/executorch-config.cmake b/tools/cmake/executorch-config.cmake
index f64b080239d..6472648786c 100644
--- a/tools/cmake/executorch-config.cmake
+++ b/tools/cmake/executorch-config.cmake
@@ -150,7 +150,9 @@ if(TARGET coremldelegate)
 endif()
 
 if(TARGET etdump)
-  set_target_properties(etdump PROPERTIES INTERFACE_LINK_LIBRARIES "flatccrt;executorch")
+  set_target_properties(
+    etdump PROPERTIES INTERFACE_LINK_LIBRARIES "flatccrt;executorch"
+  )
 endif()
 
 if(TARGET optimized_native_cpu_ops_lib)
@@ -174,13 +176,11 @@ if(TARGET extension_threadpool)
 endif()
 
 set(shared_lib_list
-  # executorch -- size tests fail due to regression if we include this and I'm not sure it's needed.
-  optimized_native_cpu_ops_lib
-  portable_ops_lib
-  quantized_ops_lib
-  xnnpack_backend
-  vulkan_backend
-  quantized_ops_aot_lib)
+    # executorch -- size tests fail due to regression if we include this and I'm
+    # not sure it's needed.
+    optimized_native_cpu_ops_lib portable_ops_lib quantized_ops_lib
+    xnnpack_backend vulkan_backend quantized_ops_aot_lib
+)
 foreach(lib ${shared_lib_list})
   if(TARGET ${lib})
     target_link_options_shared_lib(${lib})