NFC: Suppress -Wreturn-type-c-linkage warnings in GlobalExecutor.cpp.

Author: tshortli

stdlib/public/Concurrency/GlobalExecutor.cpp

@@ -135,18 +135,24 @@ void swift::swift_task_enqueueGlobalWithDeadline(
 // Implemented in Swift because we need to obtain the user-defined flags on the executor ref.
 //
 // We could inline this with effort, though.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wreturn-type-c-linkage"
 extern "C" SWIFT_CC(swift)
 SerialExecutorRef _task_serialExecutor_getExecutorRef(
         HeapObject *executor, const Metadata *selfType,
         const SerialExecutorWitnessTable *wtable);
+#pragma clang diagnostic pop
 
 // Implemented in Swift because we need to obtain the user-defined flags on the executor ref.
 //
 // We could inline this with effort, though.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wreturn-type-c-linkage"
 extern "C" SWIFT_CC(swift)
 TaskExecutorRef _task_executor_getTaskExecutorRef(
     HeapObject *executor, const Metadata *selfType,
     const SerialExecutorWitnessTable *wtable);
+#pragma clang diagnostic pop
 
 SWIFT_CC(swift)
 static bool swift_task_isOnExecutorImpl(HeapObject *executor,