support SharedArrayBuffers

[vapier]

is there any reason to disallow SharedArrayBuffers ? I'm trying to use the APIs in a threaded program, and that requires the WASM module be backed by a SharedArrayBuffer. whenever it wants to send data using its locally allocated buffers, the calls fail:

TypeError: Failed to execute 'write' on 'WritableStreamDefaultWriter': Failed to read the 'data' property from 'UDPMessage': The provided ArrayBufferView value must not be shared.
    at WebUdpSocket.sendto (sockets.js:1792:39)
    at async Background.onMessage_syscall (process.js:320:13)
    at async Background.onMessage (process.js:303:9)

this means i have to create a temporary buffer, copy the shared array buffer into it, and pass that to the write stream. this is a bit inefficient as one can imagine.