include: Fix triggering of Clang's -Wexpansion-to-defined in SDL_endian.h

It doesn't like #if statements that uses a macro that uses defined(x).

include/SDL_endian.h

@@ -93,16 +93,22 @@ extern "C" {
  */
 
 /* various modern compilers may have builtin swap */
-#define HAS_BUILTIN_BSWAP16 (_SDL_HAS_BUILTIN(__builtin_bswap16)) || \
-    (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))
-#define HAS_BUILTIN_BSWAP32 (_SDL_HAS_BUILTIN(__builtin_bswap32)) || \
-    (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
-#define HAS_BUILTIN_BSWAP64 (_SDL_HAS_BUILTIN(__builtin_bswap64)) || \
-    (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
+#if defined(__GNUC__)
+#   define HAS_BUILTIN_BSWAP16 (_SDL_HAS_BUILTIN(__builtin_bswap16)) || \
+        (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))
+#   define HAS_BUILTIN_BSWAP32 (_SDL_HAS_BUILTIN(__builtin_bswap32)) || \
+        (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
+#   define HAS_BUILTIN_BSWAP64 (_SDL_HAS_BUILTIN(__builtin_bswap64)) || \
+        (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
 
-/* this one is broken */
-#define HAS_BROKEN_BSWAP (defined(__GNUC__) && \
-    (__GNUC__ == 2 && __GNUC_MINOR__ <= 95))
+    /* this one is broken */
+#   define HAS_BROKEN_BSWAP (__GNUC__ == 2 && __GNUC_MINOR__ <= 95)
+#else
+#   define HAS_BUILTIN_BSWAP16 0
+#   define HAS_BUILTIN_BSWAP32 0
+#   define HAS_BUILTIN_BSWAP64 0
+#   define HAS_BROKEN_BSWAP 0
+#endif
 
 #if HAS_BUILTIN_BSWAP16
 #define SDL_Swap16(x) __builtin_bswap16(x)