[nailer]

stdout isn't Linux specific, and it's all that's needed.

Edit: solved this one myself with a little research. Systemd also implements the /dev/log Unix domain socket (even with the silly syslog facility names, without needing syslog installed) - so:

    global
            log /dev/log local0 info

I've added this as an answer on Stack and try and get it into the docs for anyone else.