Remove a pointless allocation

The stack size is 152 bytes which is teeny.

wayland-backend/src/rs/socket.rs

@@ -75,7 +75,7 @@ impl Socket {
         #[cfg(target_os = "macos")]
         let flags = RecvFlags::DONTWAIT;
 
-        let mut cmsg_space = vec![0; rustix::cmsg_space!(ScmRights(MAX_FDS_OUT))];
+        let mut cmsg_space = [0; rustix::cmsg_space!(ScmRights(MAX_FDS_OUT))];
         let mut cmsg_buffer = RecvAncillaryBuffer::new(&mut cmsg_space);
         let mut iov = [IoSliceMut::new(buffer)];
         let msg = retry_on_intr(|| recvmsg(&self.stream, &mut iov[..], &mut cmsg_buffer, flags))?;