split the manifest step into a separate skript

manifest.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -euxo pipefail
+. docker/env
+
+for image in ${IMAGES}; do
+  # there's no docker manifest rm command, and the create --amend does not work, so we have to clean up manually
+  rm -rf "${HOME}/.docker/manifests/docker.io_jketterl_${image}-${TAG}"
+  IMAGE_LIST=""
+  for a in $ALL_ARCHS; do
+    IMAGE_LIST="$IMAGE_LIST jketterl/$image:$TAG-$a"
+  done
+  docker manifest create jketterl/$image:$TAG $IMAGE_LIST
+  docker manifest push --purge jketterl/$image:$TAG
+  docker pull jketterl/$image:$TAG
+done