Merge pull request #35584 from compnerd/single-threaded-drain

Concurrency: support draining the main queue in single threaded mode

Author: compnerd

stdlib/public/Concurrency/Task.cpp

@@ -536,6 +536,12 @@ void swift::swift_continuation_logFailedCheck(const char *message) {
 }
 
 void swift::swift_task_asyncMainDrainQueue() {
+#if SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
+  bool Finished = false;
+  donateThreadToGlobalExecutorUntil([](void *context) {
+    return *reinterpret_cast<bool*>(context);
+  }, &Finished);
+#else
 #if defined(_WIN32)
   static void(FAR *pfndispatch_main)(void) = NULL;
 
@@ -561,4 +567,5 @@ void swift::swift_task_asyncMainDrainQueue() {
   else
     dispatch_main();
 #endif
+#endif
 }