message: use legacy texture creation for mac and linux
diff: #include <stb_image_resize.h>
  #include <variant>
  +#if PLATFORM_LINUX || PLATFORM_MAC
  +#define LEGACY_TEXTURE_CREATION 1
  +#else
  #define LEGACY_TEXTURE_CREATION 0
  +#endif
  using namespace CesiumGltf;
  