Fix ForeignLibs test for Windows (backport #10212)

[mergify]

---

This is an automatic backport of pull request #10212 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of be1ae31 has failed:

On branch mergify/bp/3.12/pr-10212
Your branch is up to date with 'origin/3.12'.

You are currently cherry-picking commit be1ae3183.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   cabal-testsuite/PackageTests/ForeignLibs/MyForeignLib.def
	modified:   cabal-testsuite/PackageTests/ForeignLibs/my-foreign-lib.cabal

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   cabal-testsuite/PackageTests/ForeignLibs/setup.test.hs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[jasagredo]

Thanks!