fix macOS builds with hidapi disabled

Fixes: https://github.com/libsdl-org/SDL/issues/11647 .

src/hidapi/SDL_hidapi.c

@@ -1242,7 +1242,7 @@ int SDL_hid_init(void)
         return -1;
     }
 
-#ifdef SDL_PLATFORM_MACOS
+#if defined(HAVE_PLATFORM_BACKEND) && !defined(SDL_HIDAPI_DISABLED)
     hid_darwin_set_open_exclusive(0);
 #endif