Bundling NixGL in a Docker image

[khazaddum]

Hi,

I have an app that uses a flake for building and it requires nixGL to run the GUI. I'm trying to bundle it in a Docker image like this:

        packages.dockerImage = let
          pkgs = import nixpkgs {
            system = system;
            overlays = [ nixgl.overlay ];
          };
        in
          pkgs.dockerTools.buildImage {
          name = "myapp";
          created = "now";
          tag = "0.1";
          copyToRoot = pkgs.buildEnv {
            paths = with pkgs; [
              self'.packages.default
              nixgl
            ];
            name = "image-root";
            pathsToLink = ["/bin"];
          };
          config = {
            Cmd = ["${pkgs.nixgl}/bin/nixGL ${self'.packages.default}/bin/myapp"];
          };
        };

This gives me an error that pkgs.nixgl is a set that can't be cast into a string. Also, if I remove the Cmd, the image is built but nixGL is not in the /bin folder or in the image's /nix/store.

What is the correct way of including nixGL in the image?