gltfio: remove locale.cpp dependency

For Android and wasm we do not use the filesystem and therefore do not
need `utils::Path`.

```
libgltfio-jni.so BEFORE 1.9 MB (693 KB gzipped)
libgltfio-jni.so AFTER  1.4 MB (542 KB gzipped)
```

android/gltfio-android/src/main/cpp/ResourceLoader.cpp

@@ -37,7 +37,7 @@ extern "C" JNIEXPORT jlong JNICALL
 Java_com_google_android_filament_gltfio_ResourceLoader_nCreateResourceLoader(JNIEnv*, jclass,
         jlong nativeEngine) {
     Engine* engine = (Engine*) nativeEngine;
-    return (jlong) new ResourceLoader({ engine, utils::Path(), true, true });
+    return (jlong) new ResourceLoader({ engine, {}, true, true });
 }
 
 extern "C" JNIEXPORT void JNICALL