RunLoop: define mac_port_t for non-Darwin targets

If `dispatch/private.h` is not available, then we fall back to forward
declaring dispatch interfaces.  One of those is the `mach_port_t` shim
typedef.

Author: compnerd

CoreFoundation/RunLoop.subproj/CFRunLoop.c

@@ -62,6 +62,9 @@ CF_INLINE uint64_t check_uint64_add(uint64_t x, uint64_t y, int32_t* err) {
 #else
 extern dispatch_queue_t _dispatch_runloop_root_queue_create_4CF(const char *_Nullable label, unsigned long flags);
 #if USE_DISPATCH_SOURCE_FOR_TIMERS
+#if !TARGET_OS_MAC
+typedef uint32_t mach_port_t;
+#endif
 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);