CI: cabal-testsuite tests fail with "double directory"

[Mikolaj]

It fails for many GHCs and OSes like so

PackageTests/NewBuild/CmdRun/Terminate/cabal.test.hs:4:1: error:
Error:     Ambiguous module name ‘System.Directory’:
      it was found in multiple packages:
      directory-1.3.8.1 directory-1.3.8.1
  |
4 | import System.Directory (removeFile)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

(e.g.,https://github.com/haskell/cabal/runs/7766731556?check_suite_focus=true and https://github.com/haskell/cabal/runs/7763827542?check_suite_focus=true) and clearing GHA cache doesn't always help (but it helps sometimes).

The test PackageTests/NewSdist/DeterministicTrivial in which I initially observed it works for me locally and works right now for tag v3.8.1.0 (https://github.com/haskell/cabal/actions/runs/2828628263). I suggest we turn off the test for now so that CI works again and people can develop their PRs in peace. Then let's diagnose. [Edit: it seems other tests are affected as well.]