quick test

CMakeLists.txt

@@ -54,8 +54,9 @@ set(CLANG_WARNINGS
 
 if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -lc++abi")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -v -stdlib=libc++")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
     set(PROJECT_WARNINGS ${CLANG_WARNINGS})
+    execute_process(COMMAND echo "#include <cstdint>\nint main () {}" | clang-9 -E --std=c++2a -stdlib=libc++ -x c++ -dM - | grep _LIBCPP_VERSION)
     target_compile_options(test_rgbcx PUBLIC ${PROJECT_WARNINGS})
 endif()
 set(CMAKE_CXX_FLAGS_DEBUG "-g")