buildEnv: support ignoreSingleFileOutputs (resumed)

[ShamrockLee]

Add option to ignore single-file output instead of failing, which would be useful to fix Mic92/nixpkgs-review#408.

Cc: @corngood

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Mic92]

Would be cool to have this because it's not possible from pure nix to know wether a derivation is a single file.

[ShamrockLee]

Would be cool to have this because it's not possible from pure nix to know wether a derivation is a single file.

I think we should enforce a policy to exclude all single-file outputs from meta.outputsToInstall for all packages exposed under pkgs with recurseIntoAttrs in the long run, but it is also crucial for buildEnv to be flexible enough to ignore those single-file outputs.

[philiptaron]

@ShamrockLee, I'd like to merge this once the merge conflict is resolved.

[nix-owners]

The PR's base branch is set to staging, but 248 commits from the master branch are included. Make sure you know the right base branch for your changes, then:

• If the changes should go to the master branch, change the base branch to master
• If the changes should go to the staging branch, rebase your PR onto the merge base with the staging branch:

  # git rebase --onto $(git merge-base upstream/staging HEAD) $(git merge-base upstream/master HEAD)
  git rebase --onto 7746ea988939fe49dfb60d917dae7ca55ba16afc cd519af995cc5fa35c594751a42a02ba6b705ee6
  git push --force-with-lease

[ShamrockLee]

@philiptaron Rebased.

[ShamrockLee]

@Mic92 @philiptaron Regarding the argument name, do you think it should be ignoreFileOutputs or ignoreSingleFileOutputs?

[philiptaron]

I'm amenable to both, but ignoreSingleFileOutputs does more clearly say what it's doing.

[ShamrockLee]

Renamed!

[philiptaron]

One copy-editing nit on a comment.

[ShamrockLee]

Rebasd and squashed the commit.