cross-compile-flake.nix

{
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-22.11";

  outputs = inputs@{ self, nixpkgs, ... }:
    let
      lib = nixpkgs.lib;

      darwin = [ "x86_64-darwin" "aarch64-darwin" ];
      linux = [ "x86_64-linux" "aarch64-linux" ];
      allSystems = darwin ++ linux;

      forEachSystem = systems: f: lib.genAttrs systems (system: f system);
      forAllSystems = forEachSystem allSystems;
    in
    {
      packages = forAllSystems (system:
        let
          pkgs = import nixpkgs { inherit system; };
        in
        {
          inherit (pkgs) hello;
          cross = forEachSystem (lib.filter (sys: sys != system) allSystems) (targetSystem:
            let
              crossPkgs = import nixpkgs { localSystem = system; crossSystem = targetSystem; };
            in
            {
              inherit (crossPkgs) hello;
            }
          );
        }
      );
    };
}