Ensure flags are applied to CVTT options

(cherry picked from commit 709aa8ae2caa3789ad88b91722ecce5a2115e6e3)

modules/cvtt/image_compress_cvtt.cpp

@@ -170,6 +170,7 @@ void image_compress_cvtt(Image *p_image, float p_lossy_quality, Image::CompressS
 	if (p_source == Image::COMPRESS_SOURCE_NORMAL) {
 		flags |= cvtt::Flags::Uniform;
 	}
+	options.flags = flags;
 
 	Image::Format target_format = Image::FORMAT_BPTC_RGBA;