Don't depend on zlib.dll on windows.

[AndreasPK]

zlib.DLL might not be available, for example if we build in a msys env, but run under powershell. Fixes #12272

---

Template B: This PR does not modify behaviour or interface

E.g. the PR only touches documentation or tests, does refactorings, etc.

Include the following checklist in your PR:

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[Mikolaj]

Thank you!

[ffaf1]

This looks uncontroversial enough to make 3.18.2.0.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-09-06 06:57 UTC · Rule: default · triggered by rule Put pull requests in the rebase+merge queue
• ✅ Checks passed · on draft merge queue: checking #12274 on master (4d36130) #12325
• ✅ Merged — 2026-09-06 09:04 UTC · at 6c8b290e0e056a9233bed3138cc63bdc7ebfc398 · merge

This pull request spent 2 hours 6 minutes 52 seconds in the queue, including 1 hour 56 minutes 26 seconds running CI.

Required conditions to merge

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  • Don't depend on zlib.dll on windows. #12274
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  • Don't depend on zlib.dll on windows. #12274
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[ffaf1]

@mergify backport 3.18

[mergify]

backport 3.18

✅ Backports have been created

Details

• #12327 Backport #12274: Don't depend on zlib.dll on windows. has been created for branch 3.18

[ulysses4ever]

no changelog entry :-( i'm not sure Template B was the right call here.

[ulysses4ever]

moreover, this patch only touched cabal.project, which means many peope won't benefit from it: neither cabal install cabal-install nor our release process, which uses another project file, cabal.release.project. @ffaf1 @Mikolaj ?

[Mikolaj]

Ouch, I missed both when reviewing. @AndreasPK: would you find a moment to make an extra-quick followup PR with the same fix for the other 3 cabal.release.* files and with the tiny changelog snippet, as in all the other PRs? Or even one of the above?

[ulysses4ever]

the other project file (there's just one that we care about i think, cabal.release.project) is easy but do we have a plan for cabal install cabal-install? If we can't make it "just work", we probably should document it somewhere?..