SDL_mslib.c: clang-cl does not support `/GL-`

CMakeLists.txt

@@ -739,10 +739,10 @@ if(MSVC)
   endif()
 endif()
 
-if(MSVC)
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
   # Due to a limitation of Microsoft's LTO implementation, LTO must be disabled for memcpy and memset.
   # The same applies to various functions normally belonging in the C library (for x86 architecture).
-  set_property(SOURCE src/stdlib/SDL_mslibc.c APPEND PROPERTY COMPILE_FLAGS /GL-)
+  set_property(SOURCE src/stdlib/SDL_mslibc.c APPEND_STRING PROPERTY COMPILE_FLAGS " /GL-")
 endif()
 
 if(SDL_ASSEMBLY)