Fixed some warnings when building on Linux with -DSDL_LIBC=OFF

src/SDL_log.c

@@ -496,6 +496,11 @@ SDL_LogOutput(void *userdata, int category, SDL_LogPriority priority,
 #if HAVE_STDIO_H && \
     !(defined(__APPLE__) && (defined(SDL_VIDEO_DRIVER_COCOA) || defined(SDL_VIDEO_DRIVER_UIKIT)))
     fprintf(stderr, "%s: %s\n", SDL_priority_prefixes[priority], message);
+#else
+    /* We won't print anything, but reference the priority prefix anyway
+       to avoid a compiler warning.
+     */
+    (void)SDL_priority_prefixes[priority];
 #endif
 }