Rewrite generate_bootstrap_plan, so that it does not require Nix

[Bodigrim]

I'd like to be able to run bootstrap/generate_bootstrap_plans without Nix, which is impossible at the moment. Is there any opposition to rewriting it to use ghcup instead of Nix?

[geekosaur]

I've never needed Nix, and maybe you've found something that isn't maintained (I don't recall it being documented).

CABAL_CONFIG=~/.config/cabal/config make generate-bootstrap-jsons

(The CABAL_CONFIG part is because I use XDG paths, and it hasn't been updated to support them yet.)

[Mikolaj]

I think @mpickering created the Nix-based bootstrap tool. There were indeed problems with the non-Nix version. Fixing them would be great. Mat may remember why it was failing for him.

[ulysses4ever]

If you want a ghcup-based version, please add, not replace the nix-based one: at least two of the current five maintainers use NixOS where ghcup doesn't work (natively).