Fix socket binding on macOS

[MadLittleMods]

Fix socket binding on macOS. Abstract namespaced sockets are only supported on Linux so moving the socket to a real temporary file.

Fix #1054

Dev notes

• https://apple.stackexchange.com/a/157509/164173
• "abstract socket name, supported only on Linux", https://docs.racket-lang.org/unix-socket/index.html

 # Clean up the socket file after we're done
   $poke_fut->on_done( sub {
      unlink($path) or die "$0: can't unlink $path: $!\n";
   });

[richvdh]

lgtm

[MadLittleMods]

Thanks @richvdh 🦗