avoid SAB when possible

[zamfofex]

When stdin is constant (or potentially empty), SharedArrayBuffer doesn’t seem necessary.

Besides that, another option would be to run Binaryen with the asyncify pass on the WebAssembly file in order to be able to run some code asynchronously. I have used Binaryen.js (from the AssemblyScript community) in the past for that effect, modifying the Wasm binary within the browser itself!

[taybenlor]

Yeah those are both interesting ideas!

I've avoided doing asyncify to keep things simple, but it's worth exploring.

Being able yo dodge SAB would really help with improving the integration experience. Changing headers is annoying.