Fix recomp bug by invalidating cache on build exception

[alt-romes]

Be sure to invalidate the cache if building throws an exception! If not, we'll abort execution with a stale recompilation cache. See ghc#24926 for an example of how this can go wrong.

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[mpickering]

I wrote this patch with Rodrigo, we diagnosed the issue was that on a build failure the file monitor contents was not invalidated. If you changed the source file back to what it was originally then compilation would be skipped (and lead to later errors).

[alt-romes]

I'm working on a test

[geekosaur]

Does this need to be backported? (It sounds to me like yes.)

[alt-romes]

Does this need to be backported? (It sounds to me like yes.)

Definitely. It's a very small, but critical, change.

[geekosaur]

@mergify backport 3.12

[mergify]

backport 3.12

✅ Backports have been created

• #10117 Fix recomp bug by invalidating cache on build exception (backport #10105) has been created for branch 3.12