Revert "[CMake] Drop libLTO and switch to PIE for Fuchsia toolchain"

This reverts commit a6f621b.

We suspect that this patch might be the culprit that is causing
every llvm executable to be sigkill'd immediately on Apple Silicon
machines. Notably, the only other cache file with CMAKE_POSITION_INDEPENDENT_CODE
is Apple's and they have it off.

Author: abrachet

clang/cmake/caches/Fuchsia-stage2.cmake

@@ -14,7 +14,6 @@ set(LLVM_ENABLE_LIBEDIT OFF CACHE BOOL "")
 set(LLVM_ENABLE_LLD ON CACHE BOOL "")
 set(LLVM_ENABLE_LTO ON CACHE BOOL "")
 set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR ON CACHE BOOL "")
-set(LLVM_ENABLE_PIC OFF CACHE BOOL "")
 set(LLVM_ENABLE_PLUGINS OFF CACHE BOOL "")
 set(LLVM_ENABLE_TERMINFO OFF CACHE BOOL "")
 set(LLVM_ENABLE_UNWIND_TABLES OFF CACHE BOOL "")
@@ -93,7 +92,6 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     list(APPEND BUILTIN_TARGETS "${target}")
     set(BUILTINS_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
-    set(BUILTINS_${target}_CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "")
     set(BUILTINS_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
@@ -106,7 +104,6 @@ foreach(target aarch64-unknown-linux-gnu;armv7-unknown-linux-gnueabihf;i386-unkn
     list(APPEND RUNTIME_TARGETS "${target}")
     set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
-    set(RUNTIMES_${target}_CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "")
     set(RUNTIMES_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
@@ -157,7 +154,6 @@ if(FUCHSIA_SDK)
     list(APPEND BUILTIN_TARGETS "${target}")
     set(BUILTINS_${target}_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
-    set(BUILTINS_${target}_CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "")
     set(BUILTINS_${target}_CMAKE_ASM_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_C_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(BUILTINS_${target}_CMAKE_CXX_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
@@ -173,7 +169,6 @@ if(FUCHSIA_SDK)
     set(RUNTIMES_${target}_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_BUILD_WITH_INSTALL_RPATH ON CACHE BOOL "")
-    set(RUNTIMES_${target}_CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "")
     set(RUNTIMES_${target}_CMAKE_ASM_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_C_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_CXX_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
@@ -293,6 +288,7 @@ set(LLVM_TOOLCHAIN_TOOLS
 set(LLVM_DISTRIBUTION_COMPONENTS
   clang
   lld
+  LTO
   clang-apply-replacements
   clang-doc
   clang-format