Update GitHub Actions workflow for Docker builds

.github/workflows/build.yml

@@ -0,0 +1,61 @@
+name: Build Container Images
+
+on:
+  push:
+    branches: [ "main" ]
+  schedule:
+    - cron: "0 4 * * *"
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_PREFIX: ${{ github.repository }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        image:
+          - name: rpmbuild
+            context: ./rpmbuild
+          - name: kernel
+            context: ./kernel
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log into registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_PREFIX }}/${{ matrix.image.name }}
+          tags: |
+            type=raw,value=latest
+            type=raw,value={{date 'YYYYMMDD'}}
+
+      - name: Build and push ${{ matrix.image.name }}
+        uses: docker/build-push-action@v5
+        with:
+          context: ${{ matrix.image.context }}
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max