chore: cross-compile docker images with buildx (#3503)

.github/workflows/ci.yaml

@@ -386,9 +386,10 @@ jobs:
       - name: Remove release packages and test artifacts
         run: rm -rf ./release-packages ./test/test-results
 
-  docker-amd64:
+  # Builds both amd64 and arm64 images
+  docker-images:
     runs-on: ubuntu-latest
-    needs: package-linux-amd64
+    needs: [package-linux-amd64, package-linux-arm64]
     steps:
       - uses: actions/checkout@v2
 
@@ -398,34 +399,16 @@ jobs:
           name: release-packages
           path: ./release-packages
 
-      - name: Run ./ci/steps/build-docker-image.sh
-        run: ./ci/steps/build-docker-image.sh
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
 
-      - name: Upload release image
-        uses: actions/upload-artifact@v2
-        with:
-          name: release-images
-          path: ./release-images
-
-  # TODO: this is the last place where we use our self-hosted arm64 runner.
-  # In the future, consider switching to docker buildx + qemu,
-  # thus removing the requirement for us to maintain the runner.
-  docker-arm64:
-    runs-on: ubuntu-arm64-latest
-    needs: package-linux-arm64
-    steps:
-      - uses: actions/checkout@v2
-
-      - name: Download release package
-        uses: actions/download-artifact@v2
-        with:
-          name: release-packages
-          path: ./release-packages
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
 
       - name: Run ./ci/steps/build-docker-image.sh
         run: ./ci/steps/build-docker-image.sh
 
-      - name: Upload release image
+      - name: Upload release images
         uses: actions/upload-artifact@v2
         with:
           name: release-images
@@ -433,7 +416,7 @@ jobs:
 
   trivy-scan-image:
     runs-on: ubuntu-20.04
-    needs: docker-amd64
+    needs: docker-images
     # NOTE@jsjoeio: disabling due to a memory issue upstream
     # See: https://github.com/github/codeql-action/issues/528
     if: 1 == 2
@@ -466,6 +449,7 @@ jobs:
         uses: github/codeql-action/upload-sarif@v1
         with:
           sarif_file: "trivy-image-results.sarif"
+
   # We have to use two trivy jobs
   # because GitHub only allows
   # codeql/upload-sarif action per job