Fix `utimesat` availability condition

As `__has_attribute` macro is always defined in internal/compilers.h,
gcc warns `-Wunguarded-availability-new` as unknown option.  Check if
the warning option is usable instead.

file.c

@@ -2930,7 +2930,7 @@ utime_failed(struct apply_arg *aa)
 # elif defined(__APPLE__) && \
     (!defined(MAC_OS_X_VERSION_13_0) || (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_13_0))
 
-#   if defined(__has_attribute) && __has_attribute(availability)
+#   if __has_attribute(availability) && __has_warning("-Wunguarded-availability-new")
 typedef int utimensat_func(int, const char *, const struct timespec [2], int);
 
 RBIMPL_WARNING_PUSH()
@@ -2945,7 +2945,7 @@ RBIMPL_WARNING_POP()
 #   define utimensat rb_utimensat()
 #   else /* __API_AVAILABLE macro does nothing on gcc */
 __attribute__((weak)) int utimensat(int, const char *, const struct timespec [2], int);
-#   endif /* defined(__has_attribute) && __has_attribute(availability) */
+#   endif /* utimesat availability */
 # endif /* __APPLE__ && < MAC_OS_X_VERSION_13_0 */
 
 static int