[Concurrency] Make deinit check test not racy

The test is checking that the task executor deinit runs after task
completes. This deinit is caused on a different thread, and thus is
racing with the main() completing. This is racy because as main() exits,
we just exit the process and may not see the deinit get printed, making
the test look like the deinit "didnt trigger" but it did, just was
"late to the party"

resolves rdar://130528198

Author: ktoso

test/Concurrency/Runtime/async_task_executor_unstructured_task_ownership.swift

@@ -11,16 +11,28 @@ import Dispatch
 import StdlibUnittest
 import _Concurrency
 
+// For sleep
+#if canImport(Darwin)
+import Darwin
+#elseif canImport(Glibc)
+import Glibc
+#elseif canImport(Android)
+import Android
+#endif
+
 final class NaiveQueueExecutor: TaskExecutor {
   let queue: DispatchQueue
+  let sem: DispatchSemaphore
 
-  init(_ queue: DispatchQueue) {
+  init(_ sem: DispatchSemaphore, _ queue: DispatchQueue) {
     print("init \(Self.self)")
+    self.sem = sem
     self.queue = queue
   }
 
   deinit {
     print("deinit \(Self.self)")
+    sem.signal()
   }
 
   public func enqueue(_ _job: consuming ExecutorJob) {
@@ -39,15 +51,16 @@ final class NaiveQueueExecutor: TaskExecutor {
 }
 
 nonisolated func nonisolatedFunc(expectedQueue queue: DispatchQueue) async {
-//  dispatchPrecondition(condition: .onQueue(queue))
+  dispatchPrecondition(condition: .onQueue(queue))
   print("Invoked: \(#function)")
 }
 
 @main struct Main {
 
   static func main() async {
     let queue = DispatchQueue(label: "example-queue")
-    var executor: NaiveQueueExecutor? = NaiveQueueExecutor(queue)
+    let deinitSem = DispatchSemaphore(value: 0)
+    var executor: NaiveQueueExecutor? = NaiveQueueExecutor(deinitSem, queue)
 
     // Task retains the executor, so it should never deinit before the task completes
     // CHECK: init NaiveQueueExecutor
@@ -75,6 +88,8 @@ nonisolated func nonisolatedFunc(expectedQueue queue: DispatchQueue) async {
     // CHECK: Task done
     // CHECK-NEXT: deinit NaiveQueueExecutor
 
+    deinitSem.wait()
+
     print("Done")
     // CHECK: Done
   }