graphics: make raw image synchronization an opt-in setting

src/common/emulatorConfig.cpp

@@ -152,6 +152,10 @@ bool ReadbackLinearImagesEnabled() {
 	return g_config->readback_linear_images;
 }
 
+bool SyncRawImageBuffersEnabled() {
+	return g_config->sync_raw_image_buffers;
+}
+
 bool TessellationEnabled() {
 	return g_config->tessellation_enabled;
 }