dispatch: exclude some mach_port_t usage

This removes some `mach_port_t` usage in the eventlink support.
Additionally guard the inclusion of a mach header with `HAVE_MACH` to
allow building on non-Apple platforms.

Author: compnerd

os/eventlink_private.h

@@ -111,6 +111,7 @@ OS_EXPORT OS_OBJECT_WARN_UNUSED_RESULT
 int
 os_eventlink_activate(os_eventlink_t eventlink);
 
+#if HAVE_MACH
 /*!
  * @function os_eventlink_extract_remote_port
  *
@@ -141,6 +142,7 @@ os_eventlink_extract_remote_port(os_eventlink_t eventlink, mach_port_t *port_out
 OS_EXPORT OS_OBJECT_RETURNS_RETAINED
 os_eventlink_t _Nullable
 os_eventlink_create_with_port(const char *name, mach_port_t mach_port);
+#endif
 
 /*!
  * @function os_eventlink_create_remote_with_eventlink

src/internal.h

@@ -252,7 +252,9 @@ upcast(dispatch_object_t dou)
 #include "channel_private.h"
 #include "workloop_private.h"
 #include "source_private.h"
+#if HAVE_MACH
 #include "mach_private.h"
+#endif
 #include "data_private.h"
 #include "time_private.h"
 #include "os/voucher_private.h"