Fix cannot find type ucred for MacOs by using fake definitions

Author: LinkTed

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

@@ -10,7 +10,7 @@ use crate::slice::from_raw_parts;
 use crate::sys::net::Socket;
 
 // FIXME(#43348): Make libc adapt #[doc(cfg(...))] so we don't need these fake definitions here?
-#[cfg(not(unix))]
+#[cfg(all(doc, not(target_os = "linux"), not(target_os = "android")))]
 #[allow(non_camel_case_types)]
 mod libc {
     pub use libc::c_int;