Properly report build errors on chrooted stores

[thufschmitt]

Motivation

When encountering a build error, Nix moves the output paths out of the chroot into their final location (for “easier debugging of build failures”). However this was broken for chroot stores as it was moving it to the logical location, not the physical one.

Fix it by moving to the physical (real) location.

Context

Fix #8395

Checklist for maintainers

Maintainers: tick if completed or explain if not relevant

• agreed on idea
• agreed on implementation strategy
• tests, as appropriate
  • functional tests - tests/**.sh
  • unit tests - src/*/tests
  • integration tests - tests/nixos/*
• documentation in the manual
• documentation in the internal API docs
• code and comments are self-explanatory
• commit message explains why the change was made
• new feature or incompatible change: updated release notes

Priorities

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[Ericson2314]

Everything looks good....except we need a test :)

[thufschmitt]

Everything looks good....except we need a test :)

Indeed. I left out the test because

1. It was a bit annoying to write, and I'm lazy
2. I'd like to first understand whether this move is useful at all, and I couldn't find where it was used. So I'd like to make sure it's the case before spending time writing a potentially useless test

[Ericson2314]

Actually is this right? Shouldn't it be the fake store dir inside the choot, but the real store dir outside the chroot?

[thufschmitt]

Actually is this right? Shouldn't it be the fake store dir inside the choot, but the real store dir outside the chroot?

Well, for the copy it definitely should be the real store dir that we want

[Ericson2314]

Right but the source dir I think should continue to be the source dir.

[github-actions]

Successfully created backport PR for 2.13-maintenance:

• [Backport 2.13-maintenance] Properly report build errors on chrooted stores #8408

[github-actions]

Backport failed for 2.13-maintenance, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin 2.13-maintenance
git worktree add -d .worktree/backport-8399-to-2.13-maintenance origin/2.13-maintenance
cd .worktree/backport-8399-to-2.13-maintenance
git checkout -b backport-8399-to-2.13-maintenance
ancref=$(git merge-base f41dd2c306a5986340b04c1635bd674e4a01b78d d16a1994fb6048d4ea48090c5aabafb7ad89c84f)
git cherry-pick -x $ancref..d16a1994fb6048d4ea48090c5aabafb7ad89c84f

[github-actions]

Successfully created backport PR for 2.15-maintenance:

• [Backport 2.15-maintenance] Properly report build errors on chrooted stores #8465