Include hash of ghc --info in cabal-hash.txt

[ElvishJerricco]

My understanding is that cabal-hash.txt includes all the details which are to be hased for Nix style local builds. Given the Nix style philosophy, it might make sense for that hash to vary with the contents of ghc --info. Certainly we wouldn't want packages to have binary dependencies on different installations of the core libraries, for example.

[hvr]

Duplicate of #5116

[23Skidoo]

Closing in favour of #5116.