Fix some concurrency tests not to run on os stdlib bots

rdar://77564014

Author: aschwaighofer

test/Concurrency/Runtime/async_task_async_let_child_cancel.swift

@@ -4,6 +4,8 @@
 // REQUIRES: concurrency
 
 // UNSUPPORTED: OS=windows-msvc
+// UNSUPPORTED: back_deployment_runtime
+// UNSUPPORTED: use_os_stdlib
 
 @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
 func printWaitPrint(_ int: Int) async -> Int {

test/Concurrency/Runtime/async_task_locals_prevent_illegal_use.swift

@@ -8,6 +8,8 @@
 // REQUIRES: executable_test
 // REQUIRES: concurrency
 // REQUIRES: libdispatch
+// UNSUPPORTED: use_os_stdlib
+// UNSUPPORTED: back_deployment_runtime
 
 @available(SwiftStdlib 5.5, *)
 enum TL {

test/Concurrency/Runtime/custom_executors.swift

@@ -5,6 +5,7 @@
 
 // UNSUPPORTED: OS=windows-msvc
 // UNSUPPORTED: back_deployment_runtime
+// UNSUPPORTED: use_os_stdlib
 
 actor Simple {
   var count = 0