[builtins] Fix -Wunused-local-typedef warning in compile time asserts
Use the __attribute__ spellings when compiling with clang-cl so that
__attribute__((unused)) expands to something.
#define AEABI_RTABI __attribute__((__pcs__("aapcs")))
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && !defined(__clang__)
#define ALWAYS_INLINE __forceinline
#define NOINLINE __declspec(noinline)
#define NORETURN __declspec(noreturn)
