add nix: apkg + CI

This depends on MR !1188 (merged) (includes it). Otherwise I think it's merge-able, but there's no need to hurry as it's mainly meant a proof of concept.

added packaging tests labels

mentioned in merge request packaging/apkg!71 (merged)

added 1 commit

• f1e4010f - ci/pkgtest: add nix

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added 1 commit

• 3c0ce18c - ci/pkgtest: add nix

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resolved all threads

marked this merge request as ready

added 3 commits

• 5c43f319 - 1 commit from branch master
• 9d293733 - distro/pkg/nix: add
• 29a25b99 - ci/pkgtest: add nix

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added 7 commits

• 29a25b99...25a7121d - 5 commits from branch master
• e69152d9 - distro/pkg/nix: add
• 3c29b74b - ci/pkgtest: add nix

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approved this merge request

mentioned in commit 5c8e5995

merged