Fix discovery of ghc-pkg

[hasufell]

Relevant:

• https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4214/
• Make ghc-pkg discoverable from ghc executable haskell/cabal#7390

Fixes #98

[hasufell]

I'm not sure how portable this is for e.g. NixOS, but I also don't care. It will work for default bindists (anything installed via ghcup, stack and probably ubuntu ppa).

[phadej]

I don't like this. I'd rather do #31 until ghc --info tells the location.

[hasufell]

I don't have a strong-opinion, especially after cabal-store-gc busted my store, so I'm currently not using it anymore. But this issue could affect other binaries as well. cabal-install also has different logic to find ghc-pkg than cabal-extras.

[phadej]

cabal-install also has different logic to find ghc-pkg than cabal-extras.

Which is (or at least was) broken, thus I didn't copy it.

[hasufell]

Which is (or at least was) broken, thus I didn't copy it.

Yeah, well, cabal-extras is broken too.

[phadej]

Yeah, well, cabal-extras is broken too.

It is, I know (#31). And this is not a fix I'd prefer. I'd rather be always specific about package databases.