images/gcb-docker-gcloud: add buildx entrypoint script

images/gcb-docker-gcloud/Dockerfile

@@ -53,6 +53,7 @@ RUN cp /qemu-bin/qemu-* /usr/bin/ && \
     rm -rf /qemu-bin
 COPY --from=qemu-image /qemu-binfmt-conf.sh /qemu-binfmt-conf.sh
 COPY --from=qemu-image /register /register
+ADD ./buildx-entrypoint.sh /buildx-entrypoint
 
 RUN apk add qemu
 

images/gcb-docker-gcloud/buildx-entrypoint.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Copyright 2021 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -euo pipefail
+
+/register --reset -p yes
+/root/.docker/cli-plugins/docker-buildx create --use
+/root/.docker/cli-plugins/docker-buildx "$@"