ci: build nixos configurations

.github/workflows/cachix.yaml

@@ -1,13 +1,16 @@
-name: "Build packages for cachix"
+name: "Populate Cachix binary cache"
 on:
   push:
     paths:
+      - '**.nix'
+      - '**.age'
       - 'pkgs/**'
       - 'flake.nix'
       - 'flake.lock'
       - '.github/workflows/*'
 jobs:
-  build:
+  build-pkgs:
+    name: Build custom Nix packages
     runs-on: ubuntu-latest
 
     strategy:
@@ -33,3 +36,27 @@ jobs:
 
     - name: Build package
       run: nix build --verbose -L .#"${{ matrix.name }}"
+
+  build-configs:
+    name: Build NixOS configurations
+    runs-on: ubuntu-latest
+    needs: [ build-pkgs ]
+
+    strategy:
+      matrix:
+        name:
+        - zephyrus
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - uses: cachix/install-nix-action@v16
+
+    - uses: cachix/cachix-action@v10
+      with:
+        name: alarsyo
+        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+        extraPullNames: "nix-community"
+
+    - name: Build package
+      run: nix build --verbose -L .#nixosConfigurations."${{ matrix.name }}".config.system.build.toplevel