Fix --program-suffix resulting in invalid symlink (backport #10056)

[mergify]

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Fixes #9919
Fixes #8823

Based on this comment.

It took me a lot of time to understand where to look at and I am still unsure this fix does not introduce side effects. I would need some guidance if improvements are needed.

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This is an automatic backport of pull request #10056 done by Mergify.

[mergify]

Cherry-pick of 8593474 has failed:

On branch mergify/bp/3.12/pr-10056
Your branch is up to date with 'origin/3.12'.

You are currently cherry-picking commit 859347426.
  (fix conflicts and run "git cherry-pick --continue")
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  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   cabal-testsuite/PackageTests/Install/ProgramAffixes/Main.hs
	new file:   cabal-testsuite/PackageTests/Install/ProgramAffixes/cabal.project
	new file:   cabal-testsuite/PackageTests/Install/ProgramAffixes/cabal.test.hs
	new file:   cabal-testsuite/PackageTests/Install/ProgramAffixes/p.cabal
	new file:   changelog.d/issue-9919

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   cabal-install/src/Distribution/Client/CmdInstall.hs

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