ioctl doesn't implement FIONREAD for wasi:socket handles

[pavelsavara]

wasi-libc/libc-bottom-half/cloudlibc/src/libc/sys/ioctl/ioctl.c

Lines 22 to 37 in 7d4d3b8

	switch (request) {
	case FIONBIO: {
	va_list ap;
	va_start(ap, request);
	socket->blocking = *va_arg(ap, const int *) ==
	0;
	va_end(ap);
	return 0;
	}
	default:
	// TODO wasi-sockets: anything else we should support?
	errno = EINVAL;
	return -1;
	}

[abrown]

cc: @badeend, @dicej

[badeend]

I think wasi-libc can implement it like:

return if state == TCP_SOCKET_STATE_CONNECTED && input_pollable.ready() { 8192 } else { 0 };

Some additional info: WebAssembly/wasi-sockets#17