* justfile, inspired from Lix.
* let foreman use the stuff from outputs, similar to what Lix does>
* mess around with PERL5LIB[1] and PATH to get tests running locally.
[1] I don't really know how `Setup` was found before tbh.
I came across https://github.com/NixOS/hydra/issues/751 and realized
that hydra-notify is responsible for creating the additional jobsets in
a declarative file. My declarative testing works in dev now.