allow building for more systems

[faezs]

Don't know if this matches the CI philosophy but happy to make changes if extra systems need to be disabled there

[faezs]

Sorry this is premature since the nix build in fact does not work due to missing libraries. investigating.

[AltGr]

Thanks a lot ; indeed the nix build has been unmaintained for a while and there is likely to be a few missing dependencies. I'm not myself a Nix user, but any fix would be greatly appreciated :)

[faezs]

Luckily I've discovered the excellent opam-nix which obviates the need for maintaining separate derivations for each unlisted dependency and just uses opam-repository to find all the pinned versions. Everything builds on my system, if you re-enable nix ci hopefully it passes too.

[AltGr]

LGTM, but I'll wait for @adelaett to review when he's back from holidays, as he knows Nix much better than I do. Thanks again.

[denismerigoux]

@adelaett will not have the time to review (article deadline). I'm merging it :)