ci: Add GitHub Action to build installer images

.github/workflows/build-installer-images.yaml

@@ -0,0 +1,34 @@
+name: Build Installer Images
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "0 0 * * 2" # run at 00:00 every Tuesday
+
+jobs:
+  build-installer-images:
+    runs-on: ubuntu-24.04-arm
+    strategy:
+      # Continue with the remaining packages if one fails
+      fail-fast: false
+
+      matrix:
+        version: ["02", "3", "4", "5"]
+
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/setup-nix-action
+
+      - name: Build image for RPi ${{ matrix.version }}
+        run: nix --accept-flake-config build .#installerImages.rpi${{ matrix.version }} --out-link installer-image-rpi${{ matrix.version }}
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v7
+        with:
+          name: nixos-installer-image-rpi${{ matrix.version }}
+          path: installer-image-rpi${{ matrix.version }}/sd-image/*.img.zst
+          retention-days: 40
+          archive: false
+          compression-level: 0
+          if-no-files-found: error
+          include-hidden-files: false