bootstrap: generate missing Setup.hs in dependencies

[robx]

This allows bootstrapping against zlib 0.6.3.0, which ships
without Setup.hs.

I hope this should generally be a more robust approach than
asking maintainers of dependencies to keep Setup.hs.

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.

Testing: I ran the bootstrap successfully locally, with the zlib version updated to 0.6.3.0.

[Mikolaj]

CI Validate windows-latest ghc-8.6.5 failed randomly with

C:\Users\RUNNER~1\AppData\Local\Temp\ghcFEDE.c: DeleteFile "\\\\?\\C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\ghcFEDE.c": permission denied (Access is denied.)

Restarting the tests.

[Mikolaj]

And now the tests pass fine. Let me remove the flaky CI combo in another PR, because it's at least the second time exactly the same test fails randombly in the same way.

[andreasabel]

Looks reasonable.

[Mikolaj]

Let me press the red button, since this needs to be backported, too. Thank you, @robx!

[fgaz]

@Mergifyio backport 3.8

[mergify]

backport 3.8

✅ Backports have been created

• #8201 bootstrap: generate missing Setup.hs in dependencies (backport #8194) has been created for branch 3.8