CoreFoundation/RunLoop: conditionalize non-portable declaration

Author: compnerd

CoreFoundation/RunLoop.subproj/CFRunLoop.c

@@ -50,7 +50,9 @@ CF_INLINE uint64_t check_uint64_add(uint64_t x, uint64_t y, int32_t* err) {
 #include <dispatch/private.h>
 #elif __HAS_DISPATCH__
 extern dispatch_queue_t _dispatch_runloop_root_queue_create_4CF(const char *_Nullable label, unsigned long flags);
+#if USE_DISPATCH_SOURCE_FOR_TIMERS
 extern mach_port_t _dispatch_runloop_root_queue_get_port_4CF(dispatch_queue_t queue);
+#endif
 extern void _dispatch_source_set_runloop_timer_4CF(dispatch_source_t source, dispatch_time_t start, uint64_t interval, uint64_t leeway);
 extern bool _dispatch_runloop_root_queue_perform_4CF(dispatch_queue_t queue);
 #endif