CI: check nix build works

[KiaraGrouwstra]

it looks like nix builds weren't checked yet so far.

i think it fails now tho, i'm now trying to bisect that (edit: see #181).

[YaLTeR]

How long does this take? I'd rather the CI time not significantly increased

[KiaraGrouwstra]

on the last succeeding commit i had nix build take 1m10s, with similar command nix flake check clocking at 2m37s. (not sure if i had much cached tho, fwiw.)

[YaLTeR]

Do you know if it's possible to make it so that failure of the nix job doesn't fail the workflow? There's continue-on-error but apparently it doesn't actually work?

[KiaraGrouwstra]

i found a comment there noting that if used on the step level the job will not be marked as failed, which seems to be what you're asking for.
i've added a commit implementing that.
let's see if that works. :)

[KiaraGrouwstra]

it does look like the nix job is just a bit slower than the test-release one

[YaLTeR]

Thanks

[YaLTeR]

Is it maybe possible to add some caching? To speed it up a little