Use multiarch/qemu-user-static:aarch64 in Cloud Build

cloudbuild.yaml

@@ -20,7 +20,7 @@ steps:
   args:
     - '-c'
     - |
-      docker run --rm --privileged multiarch/qemu-user-static --reset -p yes \
+      docker run --rm --privileged multiarch/qemu-user-static:aarch64 --reset -p yes \
       && docker build \
         -t darthsim/imgproxy:$TAG_NAME-arm64 \
         -f docker/Dockerfile \