Add ARM build in GitHub Actions

- Hint: Tried to use the plattform parameter of the build-push-action,
   however this failed with an error in the Jobs.
   Therefore, I used a matrix with the platforms.
 - The ARM build takes a long time.

.github/workflows/build-lts-container-images.yaml

@@ -15,7 +15,7 @@ jobs:
           - 5.0/fpm-alpine/Dockerfile
           - 5.0/fpm/Dockerfile
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: hadolint/hadolint-action@v1.5.0
         with:
           dockerfile: ${{ matrix.dockerfile }}
@@ -29,11 +29,20 @@ jobs:
     permissions:
       packages: write
       contents: read
+    strategy:
+      matrix:
+        platform:
+          - linux/amd64
+          - linux/arm64
     steps:
       - name: 'Check out the repo'
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
+      - name: 'Set up QEMU'
+        uses: docker/setup-qemu-action@v2
+        with:
+          platforms: 'arm64,arm'
       - name: 'Set up Docker Buildx'
-        uses: docker/setup-buildx-action@v1
+        uses: docker/setup-buildx-action@v2
         with:
           buildkitd-flags: --debug
       - name: 'Log in to DockerHub'
@@ -61,6 +70,7 @@ jobs:
           push: true
           tags: ${{ steps.metadata-apache.outputs.tags }}
           labels: ${{ steps.metadata-apache.outputs.labels }}
+          platforms: ${{ matrix.platform }}
 
       - name: 'FPM variant metadata'
         id: metadata-fpm
@@ -81,6 +91,7 @@ jobs:
           push: true
           tags: ${{ steps.metadata-fpm.outputs.tags }}
           labels: ${{ steps.metadata-apache.outputs.labels }}
+          platforms: ${{ matrix.platform }}
 
       - name: 'FPM Alpine variant metadata'
         id: metadata-fpm-alpine
@@ -101,3 +112,4 @@ jobs:
           push: true
           tags: ${{ steps.metadata-fpm-alpine.outputs.tags }}
           labels: ${{ steps.metadata-apache.outputs.labels }}
+          platforms: ${{ matrix.platform }}