Replace hard linked metadata.rmeta with a copy when finalizing the incremental compilation session dir fails

[TheHighestBit]

Fixes #151181.

Since 1.90.0, on ReFS (Windows Dev Drive) volumes finalizing the incremental compilation session directory would fail with Access is denied. (os error 5). The issue was caused by #114669, which meant that metadata.rmeta inside the session dir was a hard link to a file that was potentially being used by several other processes and ReFS seemingly refuses to rename such directories. As a fallback, we try to replace the hard linked metadata file with a copy instead, so that the rename can succeed.

I don't think adding a test for this is possible due to the lack of a ReFS runner but I added a unit test for the replace_hard_link_with_copy helper.

r? @bjorn3

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[TheHighestBit]

@rustbot ready

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[bjorn3]

@bors r+

[rust-bors]

📌 Commit 0bae8cf has been approved by bjorn3

It is now in the queue for this repository.