Investigate why 'cabal update' hasn't run properly when setting up GHC 8.2 and cabal 2.4

[andreasabel]

This test:

actions/.github/workflows/workflow.yml

Lines 45 to 47 in ed06300

	- os: ubuntu-latest
	ghc: "8.2.2"
	cabal: "2.4.1.0"

does /home/runner/.ghcup/bin/cabal update (under Setting up cabal) but it seems to not affect cabal build. Maybe there are two conflicting cabals in the PATH with different .cabal dirs?

CI run: https://github.com/haskell/actions/actions/runs/3851999748/jobs/6563739708#step:3:172
Log: 13_GHC 8.2.2, Cabal 2.4.1.0 - ubuntu-latest.txt