Pass CMAKE_C_FLAGS to the custom libc++ build too

[azharudd]

Summary

When cross-compiling, flags which are passed to the compiler-rt build should be
passed to the custom libc++ build too.

[phosek]

What about C++ flags? libc++ is a C++ library so those are likely going to be important as well. Rather than lumping both C and C++ flags together into a single variable, we should probably consider adding two new keyword arguments to add_custom_libcxx, CMAKE_C_FLAGS and CMAKE_CXX_FLAGS, and use those to pass C and C++ flags separately to libc++ build.

[azharudd]

In D49397#1166067, @phosek wrote:

What about C++ flags? libc++ is a C++ library so those are likely going to be important as well. Rather than lumping both C and C++ flags together into a single variable, we should probably consider adding two new keyword arguments to add_custom_libcxx, CMAKE_C_FLAGS and CMAKE_CXX_FLAGS, and use those to pass C and C++ flags separately to libc++ build.

That sounds reasonable. Current code doesn't deal with any C or C++ specific flags -- its primarily the target arch flags. I'll update this to handle the C/C++ flags. Thanks.

[vitalybuka]

waiting for promised update

lib/fuzzer/CMakeLists.txt

macro(partially_link_libcxx name dir arch)
     )
   endmacro()
 
   foreach(arch ${FUZZER_SUPPORTED_ARCH})
     get_target_flags_for_arch(${arch} TARGET_CFLAGS)
     set(LIBCXX_${arch}_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch})
     add_custom_libcxx(libcxx_fuzzer_${arch} ${LIBCXX_${arch}_PREFIX}
       CFLAGS ${TARGET_CFLAGS}
+             ${CMAKE_C_FLAGS}
              -D_LIBCPP_ABI_VERSION=Fuzzer
              -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS=1
              -fvisibility=hidden
       CMAKE_ARGS -DCMAKE_CXX_COMPILER_WORKS=ON
                  -DLIBCXX_ENABLE_EXCEPTIONS=OFF
                  -DLIBCXX_ENABLE_SHARED=OFF
                  -DLIBCXX_CXX_ABI=none)
     target_compile_options(RTfuzzer.${arch} PRIVATE -isystem ${LIBCXX_${arch}_PREFIX}/include/c++/v1)