New nix flake interface

[MysaaJava]

This is the file i have written to provide a real flake interface for the rocq-nix-toolbox.

You can find the website at the following location
For now, i started writing pages bundle config and troubleshoot.
I also made a logo for fun, if you want to discuss it, no problem !

This implements some parts of the roadmap issue #359

[MysaaJava]

Here are some examples of usages of this branch:

• A flake.nix for mathcomp-multinomials, a simple package

flake.nix file for mathcomp-multinomials

{
  description = "Mathcomp multinomials";

  inputs = {
    coq-nix-toolbox.url = "github:MysaaJava/coq-nix-toolbox?ref=flakes";
  };

  outputs = { self, coq-nix-toolbox }: {
    packages = coq-nix-toolbox.exportOverlays self.overlays (system: {
      default = self.packages.${system}.rocq91.rocqPackages.mathcomp-multinomials;
    });
    apps = coq-nix-toolbox.apps;
    overlays = let
      rocq91-overlay = coq-nix-toolbox.mkOverlay {
        rocqPackages.rocq-core.override.version = "9.1";
      };
      rocq92-overlay = coq-nix-toolbox.mkOverlay {
        rocqPackages.rocq-core.override.version = "9.2";
        # We override version below because 9.2 is not supported in nixpkgs for them
        rocqPackages.mathcomp.override.version = "2.5.0";
        rocqPackages.mathcomp-finmap.override.version = "2.2.2";
        rocqPackages.mathcomp-bigenough.override.version = "1.0.4";

      };
      rocq-recipes-overlay = coq-nix-toolbox.mkRocqRecipesOverlay {
        mathcomp-multinomials = ./package.nix;
      };
    in {
      rocq91 = coq-nix-toolbox.composeOverlays [ rocq-recipes-overlay rocq91-overlay ];
      rocq92 = coq-nix-toolbox.composeOverlays [ rocq-recipes-overlay rocq92-overlay ];
    };
  };
}

You can run the following commands:

nix build .#rocq91.rocqPackages.mathcomp-multinomials
nix build .#rocq92.rocqPackages.mathcomp-multinomials

• Trocq, a complex project, available for coqPackages and rocqPackages, and with some version overrides
  Available on the branch cnt-flakes
  You can run the following commands:

nix build .#rocq91.rocqPackages.trocq.examples.std
nix build .#rocq90.rocqPackages.trocq.examples.std
nix build .#rocq91.rocqPackages.trocq.std
nix build .#coq91.coqPackages.trocq.examples.hott
...
# This one does not build because HoTT is not in rocqPackages
nix build .#rocq91.rocqPackages.trocq.examples.hott
# This one does not work ! This is a bug
nix build .#coq90.coqPackages.trocq

[CohenCyril]

# This one does not work ! This is a bug
nix build .#coq90.coqPackages.trocq

this is a bug where?

[MysaaJava]

There is a bug in nixpkgs making it so we have to set coqPackages.coq.override.version AND rocqPackages.rocq-core.override.version.
This is the same in the master branch of coq-nix-toolbox.

However, i was not able to reproduce the fix in my flake.