feat: add eval workflow (again)

.forgejo/workflows/eval.yml

@@ -0,0 +1,45 @@
+name: Evaluate configurations
+
+on:
+  push:
+
+jobs:
+  get-names:
+    name: Get machine names
+    runs-on: ubuntu-latest
+
+    outputs:
+      machines: ${{ steps.machines.outputs.machines }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v30
+
+      - name: Get machine names
+        id: machines
+        run: |
+          names=$(nix eval --json .#nixosConfigurations --apply 'builtins.attrNames')
+          echo "machines=$names" >> "$GITHUB_OUTPUT"
+
+  eval:
+    name: Evaluate configuration
+    runs-on: ubuntu-latest
+    needs: get-names
+
+    strategy:
+      matrix:
+        machine: ${{ fromJSON(needs.get-names.outputs.machines) }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v30
+
+      - name: Eval config
+        run: |
+          nix eval --raw .#nixosConfigurations.${{ matrix.machine }}.config.system.build.toplevel