Storage Foundation emscripten filesystem for multi-threaded apps not working

Re: the experimental https://github.com/fivedots/storage-foundation-api-emscripten-fs. I found the example app works.

But, when I try to use in my multi-threaded wasm app, the filesystem calls proxy to the main thread, and then attempt to use `openSync` and `getAllSync` which are only available from a Web Worker.

I believe this is because `getAllSync` is invoked from `lookup()`, which is invoked by calls like `___sys_stat64`. And, those calls are marked to use the proxy mechanism. The first thing that `___sys_stat64` does is to proxy to the main thread.

The problem seems a bit tricky. Calls like `__sys_stat64` do need to proxy for some posix calls. But, not for nativeio.