Setup ci on gitlab
This is not the ideal setup, but it's a start.
I'd rather not have the tests split out like this but when they aren't,everything after the first test fails with mounting /dev/vda on /mnt-root/ failed: No such file or directory
. I don't know what that's about. Check it out here: https://gitlab.com/eqyiel/nixos-mailserver/-/jobs/90278230
These also failed when I tested them, but for a different reason (timeouts). @griff has made a PR to increase the DefaultTimeoutStartSec for tests: https://github.com/NixOS/nixpkgs/pull/44916