Meta: Add Clang support to the CMake build scripts

Author: https://github.com/BertalanD
Commit: 13e3df41de
Pull-request: https://github.com/SerenityOS/serenity/pull/8718
Issue: https://github.com/SerenityOS/serenity/issues/363
Reviewed-by: https://github.com/gunnarbeutner ✅
Reviewed-by: https://github.com/nico

Meta/CMake/utils.cmake

@@ -51,6 +51,9 @@ function(serenity_libc target_name fs_name)
     add_library(${target_name} SHARED ${SOURCES})
     install(TARGETS ${target_name} DESTINATION usr/lib)
     set_target_properties(${target_name} PROPERTIES OUTPUT_NAME ${fs_name})
+    if (USE_CLANG_TOOLCHAIN)
+        target_link_libraries(${target_name} clang_rt.builtins-${SERENITY_CLANG_ARCH})
+    endif()
     target_link_directories(LibC PUBLIC ${CMAKE_CURRENT_BINARY_DIR})
     serenity_generated_sources(${target_name})
 endfunction()