message: gltfpack: Merge index streams when compression is disabled
  In the future the plan is to improve index codec so that it can handle
  concatenated index streams without issues, for now let's merge index
  streams when there's no penalty for doing so.
diff: @@ -2063,7 +2063,10 @@ size_t writeMeshIndices(std::vector<BufferView>& views, std::string& json_access
  std::string scratch;
  StreamFormat format = writeIndexStream(scratch, mesh.indices);
  - size_t view = getBufferView(views, BufferView::Kind_Index, -1, format.stride, settings.compress);
  + // note: we prefer to merge all index streams together; however, index codec currently doesn't handle concatenated index streams well and loses compression ratio
  + int variant = settings.compress ? -1 : 0;
  +
  + size_t view = getBufferView(views, BufferView::Kind_Index, variant, format.stride, settings.compress);
  size_t offset = views[view].data.size();
  views[view].data += scratch;
  