Test failures on Alpine

On alpine x86_64, the following test fails:

* cabal-testsuite/PackageTests/Backpack/T5634/setup.test.hs

CI: https://github.com/stable-haskell/cabal/actions/runs/16065635741/job/45340648767

Log: https://gist.github.com/hasufell/a4f13cd9c994d6adfcab51230c7543ed

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On ARM, the following tests fail:

* ~~cabal-testsuite/PackageTests/ProfLate/cabal.test.hs~~
* ~~cabal-testsuite/PackageTests/ProfShared/setup.test.hs~~
* cabal-testsuite/PackageTests/Backpack/T5634/setup.test.hs

CI: https://github.com/stable-haskell/cabal/actions/runs/16065635741/job/45339864618

Logs: https://gist.github.com/hasufell/86dc869f8ceb669e1a210c228199a9f8

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I have been using GHC-9.6.7 for the tests. But it uses the in-tree Cabal library. Some of the GHC bindists are also "unofficial", so a distribution issue can't be ruled out.

Start with cabal-testsuite/PackageTests/Backpack/T5634/setup.test.hs and reproduce the failures on Alpine x86_64 and ARM using GHC-9.6.7. Compare the linked CI jobs and supplied logs, while checking the in-tree Cabal library and bindist provenance. Done means determining whether the failure is Cabal-related or distribution-specific and resolving the remaining test failure; pull request #11112 is already merged.

Written by the indexing model from the issue text.