message: Add missing JNI impl
diff: @@ -239,6 +239,14 @@ Java_com_google_android_filament_gltfio_AssetLoader_nCreateInstancedAsset(JNIEnv
  return asset;
  }
  +extern "C" JNIEXPORT jlong JNICALL
  +Java_com_google_android_filament_gltfio_AssetLoader_nCreateInstance(JNIEnv* env, jclass,
  + jlong nativeLoader, jlong nativeAsset) {
  + AssetLoader* loader = (AssetLoader*) nativeLoader;
  + FilamentAsset* primary = (FilamentAsset*) nativeAsset;
  + return (jlong) loader->createInstance(primary);
  +}
  +
  extern "C" JNIEXPORT void JNICALL
  Java_com_google_android_filament_gltfio_AssetLoader_nEnableDiagnostics(JNIEnv*, jclass,
  jlong nativeLoader, jboolean enable) {
  