[libc++abi] Use target_compile_options to pass LIBCXXABI_ADDITIONAL_C…

…OMPILE_FLAGS (#96112)

We use target_compile_options to pass the libc++ variant of this flag,
so we should be consistent for libc++abi. This is actually not only a
matter of consistency: target_compile_options handles duplicate CMake
options in a certain way (it removes duplicates but has an escape hatch
using the "SHELL:" prefix), and it is important for both libc++ and
libc++abi options to be handled in the same way.

libcxxabi/CMakeLists.txt

@@ -244,7 +244,6 @@ if (${CMAKE_SYSTEM_NAME} MATCHES "AIX")
   add_flags_if_supported("-mdefault-visibility-export-mapping=explicit")
   set(CMAKE_AIX_EXPORT_ALL_SYMBOLS OFF)
 endif()
-add_compile_flags("${LIBCXXABI_ADDITIONAL_COMPILE_FLAGS}")
 add_library_flags("${LIBCXXABI_ADDITIONAL_LIBRARIES}")
 
 # Configure compiler. Must happen after setting the target flags.

libcxxabi/src/CMakeLists.txt

@@ -182,6 +182,7 @@ set_target_properties(cxxabi_shared_objects
 if (CMAKE_POSITION_INDEPENDENT_CODE OR NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
   set_target_properties(cxxabi_shared_objects PROPERTIES POSITION_INDEPENDENT_CODE ON) # must set manually because it's an object library
 endif()
+target_compile_options(cxxabi_shared_objects PUBLIC "${LIBCXXABI_ADDITIONAL_COMPILE_FLAGS}")
 
 if (LIBCXXABI_ENABLE_SHARED)
   add_library(cxxabi_shared SHARED)
@@ -261,6 +262,7 @@ set_target_properties(cxxabi_static_objects
     CXX_STANDARD_REQUIRED OFF # TODO: Make this REQUIRED once we don't need to accommodate the LLVM documentation builders using an ancient CMake
     COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS}"
 )
+target_compile_options(cxxabi_static_objects PUBLIC "${LIBCXXABI_ADDITIONAL_COMPILE_FLAGS}")
 
 if(LIBCXXABI_HERMETIC_STATIC_LIBRARY)
   target_add_compile_flags_if_supported(cxxabi_static_objects PRIVATE -fvisibility=hidden)