Fix build by adding Qemu

.github/workflows/build+test.yml

@@ -49,6 +49,9 @@ jobs:
           username: neale
           password: ${{ secrets.DOCKER_TOKEN }}
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
       # Currently required, because buildx doesn't support auto-push from docker
       - name: Set up builder
         uses: docker/setup-buildx-action@v1