Add workflow to build container

.github/workflows/container.yml

@@ -0,0 +1,58 @@
+name: Build container
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+  # Allow for manually running
+  workflow_dispatch:
+    inputs:
+      container_tag:
+        description: Tag for container
+        default: "latest"
+        required: true
+
+jobs:
+  container:
+    runs-on: ubuntu-20.04
+    env:
+      CONTAINER_NAME: ghcr.io/${{ github.repository }}
+      BUILD_PLATFORMS: linux/amd64,linux/arm,linux/arm64,linux/ppc64le,linux/s390x
+      RAW_CONTAINER_TAG: ${{ github.event.inputs.container_tag || github.event.pull_request.head.ref || 'latest' }}
+
+    steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v2.0.0
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      # Needed for buildx gha cache to work
+      - name: Expose GitHub Runtime
+        uses: crazy-max/ghaction-github-runtime@v2
+
+      - name: Build container
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          CONTAINER_TAG=$(echo "$RAW_CONTAINER_TAG" | sed 's/[^a-zA-Z0-9]\+/-/')
+
+          docker buildx build \
+            --platform "$BUILD_PLATFORMS" \
+            --tag "$CONTAINER_NAME:$CONTAINER_TAG" \
+            --cache-from type=gha \
+            --cache-to type=gha,mode=max \
+            --pull --push .