Revert "Temporarily re-apply https://reviews.llvm.org/D74347"

This reverts commit 0197eac.

The changes break Armv7/Aarch64 toolchain builders:
* http://lab.llvm.org:8011/builders/llvm-clang-win-x-armv7l/builds/5570
* http://lab.llvm.org:8011/builders/llvm-clang-win-x-aarch64/builds/5600

clang/cmake/caches/CrossWinToARMLinux.cmake

@@ -83,9 +83,6 @@ set(LIBCXX_USE_COMPILER_RT                  ON CACHE BOOL "")
 set(LIBCXX_TARGET_TRIPLE                    "${CMAKE_C_COMPILER_TARGET}" CACHE STRING "")
 set(LIBCXX_SYSROOT                          "${DEFAULT_SYSROOT}" CACHE STRING "")
 set(LIBCXX_ENABLE_SHARED                    OFF CACHE BOOL "")
-set(LIBCXX_CXX_ABI                          "libcxxabi" CACHE STRING "")
-set(LIBCXX_CXX_ABI_INCLUDE_PATHS            "${CMAKE_SOURCE_DIR}/../libcxxabi/include" CACHE PATH "")
-set(LIBCXX_CXX_ABI_LIBRARY_PATH             "${CMAKE_BINARY_DIR}/lib/${CMAKE_C_COMPILER_TARGET}/c++" CACHE PATH "")
 
 set(BUILTINS_CMAKE_ARGS                     "-DCMAKE_SYSTEM_NAME=Linux;-DCMAKE_AR=${CMAKE_AR}" CACHE STRING "")
 set(RUNTIMES_CMAKE_ARGS                     "-DCMAKE_SYSTEM_NAME=Linux;-DCMAKE_AR=${CMAKE_AR}" CACHE STRING "")