add nixos-generators module

Signed-off-by: cy <cy@cy7.sh>

.github/workflows/build-packages.yml

@@ -23,10 +23,11 @@ jobs:
     steps:
       - name: Install Nix
         uses: cachix/install-nix-action@v30
+        with:
+          install_url: https://releases.nixos.org/nix/nix-2.25.4/install
+          extra_nix_config: 'accept-flake-config = true'
       - name: Sync repository
         uses: actions/checkout@v4
-        with:
-          persist-credentials: false
       - uses: cachix/cachix-action@v14
         with:
           name: cything
@@ -57,3 +58,7 @@ jobs:
           # always save the cache
           save-always: true
       - run: nix build -L ${{ matrix.package }}
+      - uses: actions/upload-artifact@v4
+        with:
+          name: nix-${{ runner.os }}-${{ hashFiles('**/*.nix', 'flake.lock') }}
+          path: result/