Revert llvm#76246 and llvm#76083

These cause test build failures on Windows.

This reverts the following commits:
  57ca748
  d06ae33

Author: mysterymath

.github/workflows/libcxx-build-and-test.yaml

@@ -35,6 +35,7 @@ concurrency:
 
 
 env:
+  CMAKE: "/opt/bin/cmake"
   # LLVM POST-BRANCH bump version
   # LLVM POST-BRANCH add compiler test for ToT - 1, e.g. "Clang 17"
   # LLVM RELEASE bump remove compiler ToT - 3, e.g. "Clang 15"
@@ -168,18 +169,24 @@ jobs:
           'bootstrapping-build'
         ]
         machine: [ 'libcxx-runners-8-set' ]
+        std_modules: [ 'OFF' ]
         include:
         - config: 'generic-cxx26'
           machine: libcxx-runners-8-set
+          std_modules: 'ON'
         - config: 'generic-asan'
           machine: libcxx-runners-8-set
+          std_modules: 'OFF'
         - config: 'generic-tsan'
           machine: libcxx-runners-8-set
+          std_modules: 'OFF'
         - config: 'generic-ubsan'
           machine: libcxx-runners-8-set
+          std_modules: 'OFF'
         # Use a larger machine for MSAN to avoid timeout and memory allocation issues.
         - config: 'generic-msan'
           machine: libcxx-runners-8-set
+          std_modules: 'OFF'
     runs-on: ${{ matrix.machine }}
     steps:
       - uses: actions/checkout@v4
@@ -189,6 +196,7 @@ jobs:
           CC: clang-18
           CXX: clang++-18
           ENABLE_CLANG_TIDY: "OFF"
+          ENABLE_STD_MODULES: ${{ matrix.std_modules }}
       - uses: actions/upload-artifact@v3
         if: always()
         with:

libcxx/CMakeLists.txt

@@ -124,6 +124,12 @@ option(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS
    the shared library they shipped should turn this on and see `include/__availability`
    for more details." OFF)
 option(LIBCXX_ENABLE_CLANG_TIDY "Whether to compile and run clang-tidy checks" OFF)
+# TODO MODULES Remove this option and test for the requirements (CMake/Clang) instead.
+option(LIBCXX_ENABLE_STD_MODULES
+   "Whether to enable the building the C++23 `std` module. This feature is
+    experimental and has additional dependencies. Only enable this when
+    interested in testing or developing this module. See
+    https://libcxx.llvm.org/Modules.html for more information." OFF)
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
@@ -773,6 +779,7 @@ config_define_if_not(LIBCXX_ENABLE_RANDOM_DEVICE _LIBCPP_HAS_NO_RANDOM_DEVICE)
 config_define_if_not(LIBCXX_ENABLE_LOCALIZATION _LIBCPP_HAS_NO_LOCALIZATION)
 config_define_if_not(LIBCXX_ENABLE_UNICODE _LIBCPP_HAS_NO_UNICODE)
 config_define_if_not(LIBCXX_ENABLE_WIDE_CHARACTERS _LIBCPP_HAS_NO_WIDE_CHARACTERS)
+config_define_if_not(LIBCXX_ENABLE_STD_MODULES _LIBCPP_HAS_NO_STD_MODULES)
 config_define_if_not(LIBCXX_ENABLE_TIME_ZONE_DATABASE _LIBCPP_HAS_NO_TIME_ZONE_DATABASE)
 config_define_if_not(LIBCXX_ENABLE_VENDOR_AVAILABILITY_ANNOTATIONS _LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
 
@@ -856,15 +863,19 @@ endfunction()
 add_subdirectory(include)
 add_subdirectory(src)
 add_subdirectory(utils)
-add_subdirectory(modules)
+if (LIBCXX_ENABLE_STD_MODULES)
+  add_subdirectory(modules)
+endif()
 
 set(LIBCXX_TEST_DEPS "cxx_experimental")
 
 if (LIBCXX_ENABLE_CLANG_TIDY)
   list(APPEND LIBCXX_TEST_DEPS cxx-tidy)
 endif()
 
-list(APPEND LIBCXX_TEST_DEPS generate-cxx-modules)
+if (LIBCXX_ENABLE_STD_MODULES)
+  list(APPEND LIBCXX_TEST_DEPS generate-cxx-modules generate-test-module-std)
+endif()
 
 if (LIBCXX_INCLUDE_BENCHMARKS)
   add_subdirectory(benchmarks)

libcxx/cmake/caches/Generic-cxx26.cmake

@@ -1,2 +1,3 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "std=c++26" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-hardening-mode-extensive.cmake

@@ -1 +1,2 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_HARDENING_MODE "extensive" CACHE STRING "")

libcxx/cmake/caches/Generic-no-exceptions.cmake

@@ -1,2 +1,3 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-experimental.cmake

@@ -1,2 +1,3 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "enable_experimental=False" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-no-filesystem.cmake

@@ -1 +1,2 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-localization.cmake

@@ -1 +1,2 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_LOCALIZATION OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-random_device.cmake

@@ -1 +1,2 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-threads.cmake

@@ -1,3 +1,4 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK OFF CACHE BOOL "")