[compiler-rt] Force ABI to libcxxabi when building cxustom libc++

[dim]

Summary

Follow-up to 458ead66dc37, which replaced the bespoke CMakeLists.txt
file for building a custom instrumented libc++ with an invocation of the
runtimes build.

In the the bespoke CMakeLists.txt, the LIBCXX_CXX_ABI setting was forced
to libcxxabi, but this was not done for the CMake invocation for the
runtimes build. This would cause CMake configuration issues on platforms
where the default LIBCXX_CXX_ABI setting is not libcxxabi, such as
FreeBSD.

Add -DLIBCXX_CXX_ABI=libcxxabi to that invocation, to make sure the
custom instrumented libc++ always uses the expected ABI.

[phosek]

LGTM

compiler-rt/cmake/Modules/AddCompilerRT.cmake

638–642

Nit: can you move it down so that all libc++ options are kept together?

[dim]

compiler-rt/cmake/Modules/AddCompilerRT.cmake

638–642

Ah sure, it looked to me like it belonged to the libcxxabi options, but indeed it is actually a LIBCXX_* option!

compiler-rt/cmake/Modules/AddCompilerRT.cmake

ExternalProject_Add(${name}
     CMAKE_ARGS ${CMAKE_PASSTHROUGH_VARIABLES}
                ${compiler_args}
                -DCMAKE_C_FLAGS=${LIBCXX_C_FLAGS}
                -DCMAKE_CXX_FLAGS=${LIBCXX_CXX_FLAGS}
                -DCMAKE_BUILD_TYPE=Release
                -DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY
                -DLLVM_PATH=${LLVM_MAIN_SRC_DIR}
                -DLLVM_ENABLE_RUNTIMES=libcxx|libcxxabi
                -DLIBCXXABI_ENABLE_SHARED=OFF
                -DLIBCXXABI_HERMETIC_STATIC_LIBRARY=ON
                -DLIBCXXABI_INCLUDE_TESTS=OFF
+               -DLIBCXX_CXX_ABI=libcxxabi
                -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=OFF
                -DLIBCXX_ENABLE_SHARED=OFF
                -DLIBCXX_HERMETIC_STATIC_LIBRARY=ON
                -DLIBCXX_INCLUDE_BENCHMARKS=OFF
                -DLIBCXX_INCLUDE_TESTS=OFF
                -DLIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON
                ${LIBCXX_CMAKE_ARGS}
     INSTALL_COMMAND ""
     STEP_TARGETS configure build