Add ISO build workflow

.github/workflows/build_iso.yml

@@ -0,0 +1,62 @@
+name: Build Cosmic ISOs
+on:
+  workflow_dispatch:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - '.github/workflows/build_iso.yml'
+
+env:
+  IMAGE_REGISTRY: ghcr.io/${{ github.repository_owner }}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  build-iso:
+    runs-on: ubuntu-22.04
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+    container:
+      image: fedora:${{ matrix.major_version }}
+      options: "--privileged"
+      volumes:
+        - "/:/host"
+    strategy:
+      fail-fast: false
+      matrix:
+        image_name: [cosmic-silverblue, cosmic-base]
+        image_tag: [40-amd64, rawhide-amd64]
+        include:
+          - image_tag: 40-amd64
+            major_version: 40
+          - image_tag: rawhide-amd64
+            major_version: 41 # We use F41 for rawhide
+
+    steps:
+      - name: Build ISOs
+        uses: ublue-os/[email protected]
+        id: build
+        with:
+          ARCH: ${{ contains(matrix.image_tag, 'amd64') && 'x86_64' || 'arm64' }}
+          IMAGE_NAME: ${{ matrix.image_name }}
+          IMAGE_REPO: ghcr.io/ublue-os
+          VARIANT: 'Silverblue'
+          VERSION: ${{ matrix.major_version }}
+          IMAGE_TAG: ${{ matrix.image_tag }}
+          SECURE_BOOT_KEY_URL: 'https://github.com/ublue-os/akmods/raw/main/certs/public_key.der'
+          ENROLLMENT_PASSWORD: 'ublue-os'
+
+      - name: Upload ISOs and Checksum to Job Artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.image_name }}-${{ matrix.image_tag }}-${{ matrix.major_version}}
+          path: ${{ steps.build.outputs.output-directory }}
+          if-no-files-found: error
+          retention-days: 0
+          compression-level: 0
+          overwrite: true