queue: expose _dispatch_get_main_queue_port_4CF

This was being re-implemented in CF by means of a macro.  Just expose
the function instead.

Author: compnerd

private/private.h

@@ -196,12 +196,10 @@ typedef void *dispatch_runloop_handle_t;
 #error "runloop support not implemented on this platform"
 #endif
 
-#if TARGET_OS_MAC
 API_AVAILABLE(macos(10.6), ios(4.0))
 DISPATCH_EXPORT DISPATCH_CONST DISPATCH_WARN_RESULT DISPATCH_NOTHROW
 dispatch_runloop_handle_t
 _dispatch_get_main_queue_port_4CF(void);
-#endif
 
 API_AVAILABLE(macos(10.12), ios(10.0), tvos(10.0), watchos(3.0))
 DISPATCH_EXPORT DISPATCH_NOTHROW

src/queue.c

@@ -6368,13 +6368,11 @@ _dispatch_get_main_queue_handle_4CF(void)
 	return _dispatch_runloop_queue_get_handle(dq);
 }
 
-#if TARGET_OS_MAC
 dispatch_runloop_handle_t
 _dispatch_get_main_queue_port_4CF(void)
 {
 	return _dispatch_get_main_queue_handle_4CF();
 }
-#endif
 
 static bool main_q_is_draining;