Fix docs for MacOs (again)

Author: LinkTed

library/std/src/sys/unix/ext/net/datagram.rs

@@ -746,7 +746,8 @@ impl UnixDatagram {
     ///
     /// # Examples
     ///
-    /// ```no_run
+    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
+    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::UnixDatagram;
     ///