Fix failure to find package when a dependency is shared between projects (#5680)

[borsboom]

This fixes a regression that was introduced in f641880 (the fix for #5578). Now, a package will be reconfigured if the project it's being built from (and therefore the local package database it gets installed to) changes.

• Any changes that could be relevant to users have been recorded in the ChangeLog.md
• The documentation has been updated, if necessary. (N/A)

How I tested:

• A new integration test is added in test/integration/tests/5680-share-package-across-projects

[borsboom]

@snoyberg Now, in addition to the file stack-cabal-mod and stack-setup-config-mod files written to the package to track modification times, a new stack-project-root file gets written containing the project root when it was last built. I wonder if it would make sense to consolidate all this information into a single JSON or YAML file rather than writing separate files?

[istathar]

Built and tested locally (with lts-18.25 as it happens) and as far as I can tell the problem we encountered is no longer occurring, at least not using the jumping around that I demonstrated to you. I'll keep using this Stack binary through the next couple days on our main project to see if things stay sane but looking good!

Great work @borsboom and @drone-rites!

[drone29a]

This is great news, thanks for fixing! I'll also switch to this branch for local use until this fix makes it's way to a release.

[qrilka]

@borsboom I think single JSON makes sense

[snoyberg]

Nice work and nice integration test! Sorry for breaking this.

And yes, I think putting everything into a single JSON is cleaner, but it wouldn't be a blocker.

My recommendation would be cutting a release once this is merged and has at least a bit of testing.

[istathar]

@snoyberg I've been testing this for a week and it's been good; @dmvianna was not using it and just hit the bug, tried building Stack from master and the problem went away. Thank you so much for getting @borsboom to look on this. We'd be keen for a 2.7.4 release whenever you're ready.

[snoyberg]

@borsboom is planning on a release later this week. I believe it will be 2.7.5.

[borsboom]

@istathar Now released here: https://github.com/commercialhaskell/stack/releases/tag/v2.7.5