ci: build arm64 image, ensure concurency for deploy

.github/workflows/build.yaml

@@ -51,13 +51,15 @@ jobs:
           file: build/Dockerfile
           context: .
           push: ${{ github.event_name != 'pull_request' }}
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
 
   deploy:
     runs-on: ubuntu-latest
     needs: build
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
     steps:
       - name: Checkout
         uses: actions/checkout@v2