Support nix-output-manager out of the box

[doronbehar]

Hello!

Very nice project :) It would be interesting if this tool, for it's nixos-rebuild equivalent, it'd support using nom if it is available.

Best.

[water-sucks]

Hi! Thanks for checking this out, and for the feature request.

A lot of people seem to want this, so I'll be down to implement support for this when I have some downtime.

I personally don't prefer using nom, but I presume using it by default, and adding an option in the config to disable nom usage is probably an OK way for going about this.

[water-sucks]

@doronbehar I've implemented basic support for the nixos apply command to use nom as an alternate builder, both as a CLI flag and as a configuration option in cbae044.

It falls back to using Nix to build if nom is not found, unless --use-nom is specified explicitly.