Update ghc.nix instructions, pointing to the new home of ghc.nix

[sgraf812]

Initialising the flake template

[int-index]

Thanks, but could you not assume the use of direnv?

[int-index]

Also I'm getting this error when I try the new command

$ nix flake init -t git+https://gitlab.haskell.org/ghc/ghc.nix
warning: redirecting to https://gitlab.haskell.org/ghc/ghc.nix.git/
fatal: not a git repository: '.'
error:
       … while fetching the input 'git+https://gitlab.haskell.org/ghc/ghc.nix'

       error: program 'git' failed with exit code 128

[int-index]

This worked:

$ nix flake init -t git+https://gitlab.haskell.org/ghc/ghc.nix.git

but it pollutes the repo with .envrc and flake.nix. What about

$ nix develop git+https://gitlab.haskell.org/ghc/ghc.nix.git -c $SHELL

[sgraf812]

Great idea! I added a commit that adds your suggestion.