Issue building linux kernel modules after Flake update

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it’s to do with using the old version of nix, somehow i must have upgraded my version of nix resolving the issue

tested via podman run -it nixos/nix:2.18.5 sh

[nix-shell:~]$ cat flake.nix
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  };

  outputs = {nixpkgs, ...}: {
    nixosConfigurations.minimal = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        {
          boot.loader.grub.enable = false;
          fileSystems."/" = {
            device = "none";
            fsType = "tmpfs";
          };
          system.stateVersion = "25.05";
        }
      ];
    };
  };
}

[nix-shell:~]$ nix --version
nix (Nix) 2.18.5

[nix-shell:~]$ nix build .#nixosConfigurations.minimal.config.system.build.toplevel --extra-experimental-features nix-command --extra-experimental-features flakes
error: path '/nix/store/8lbv65x6gmjmrigpn7xb37wxdhb08whw-linux-6.12.20-modules-shrunk/lib' is not in the Nix store