Reproduce issue #13194 on the Wasm Workers API

[kleisauke]

See #13194

See:
#18171 (comment)

/cc @juj

[kleisauke]

It looks like PR #26489 is going to fix this.

[sbc100]

Oh nice.. I'll see if can copy this test into my PR.

[kleisauke]

Great! Based on my comment in #18171 (comment), it seems this may also require setting libc.threaded / libc.need_locks, as well as the file locks for stdin, stdout and stderr when the first worker is created.

emscripten/system/lib/pthread/pthread_create.c

Lines 130 to 138 in b7c5169

	if (!libc.threaded) {
	for (FILE *f=*__ofl_lock(); f; f=f->next)
	init_file_lock(f);
	__ofl_unlock();
	init_file_lock(__stdin_used);
	init_file_lock(__stdout_used);
	init_file_lock(__stderr_used);
	libc.threaded = 1;
	}

emscripten/system/lib/pthread/pthread_create.c

Lines 246 to 249 in b7c5169

	// Set libc.need_locks before calling __pthread_create_js since
	// by the time it returns the thread could be running and we
	// want libc.need_locks to be set from the moment it starts.
	if (!libc.threads_minus_1++) libc.need_locks = 1;