pthread: Enable the noleakcheck mark also for PROXY_TO_PTHREAD

In addition to the existing OFFSCREENCANVAS_SUPPORT configuration,
PROXY_TO_PTHREAD now also performs memory allocation internally for use by
activeSelectCallbacks.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

Author: ktock

src/lib/libpthread.js

@@ -756,7 +756,7 @@ var LibraryPThread = {
   $pthreadCreateProxied__deps: ['__pthread_create_js'],
   $pthreadCreateProxied: (pthread_ptr, attr, startRoutine, arg) => ___pthread_create_js(pthread_ptr, attr, startRoutine, arg),
 
-#if OFFSCREENCANVAS_SUPPORT
+#if OFFSCREENCANVAS_SUPPORT || PROXY_TO_PTHREAD
   // ASan wraps the emscripten_builtin_pthread_create call in
   // __lsan::ScopedInterceptorDisabler.  Unfortunately, that only disables it on
   // the thread that made the call.  __pthread_create_js gets proxied to the