prow needs some additional setup for docker buildx

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

test/build-test-images.sh

@@ -23,6 +23,7 @@ set -o nounset
 set -o pipefail
 
 source $(dirname "${BASH_SOURCE[0]}")/build-utils.sh
+source $(dirname "${BASH_SOURCE[0]}")/init-buildx.sh
 cd "${ROOT}"
 
 # ignore errors if the image already exists

test/init-buildx.sh

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+
+#   Copyright The containerd 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.
+
+# Copyright 2020 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 -o errexit
+set -o nounset
+set -o pipefail
+
+export DOCKER_CLI_EXPERIMENTAL=enabled
+# Expected builder output
+#
+# Name:   containerd-buildkit-multiarch
+# Driver: docker-container
+#
+# Nodes:
+# Name:      containerd-buildkit-multiarch0
+# Endpoint:  unix:///var/run/docker.sock
+# Status:    running
+# Platforms: linux/amd64, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/arm/v7, linux/arm/v6
+current_builder="$(docker buildx inspect)"
+
+# We can skip setup if the current builder already has multi-arch
+# AND if it isn't the "docker" driver, which doesn't work
+#
+# From https://docs.docker.com/buildx/working-with-buildx/#build-with-buildx:
+# "You can run Buildx in different configurations that are exposed through a
+# driver concept. Currently, Docker supports a “docker” driver that uses the
+# BuildKit library bundled into the docker daemon binary, and a
+# “docker-container” driver that automatically launches BuildKit inside a
+# Docker container.
+#
+# The user experience of using Buildx is very similar across drivers.
+# However, there are some features that are not currently supported by the
+# “docker” driver, because the BuildKit library which is bundled into docker
+# daemon uses a different storage component. In contrast, all images built with
+# the “docker” driver are automatically added to the “docker images” view by
+# default, whereas when using other drivers, the method for outputting an image
+# needs to be selected with --output."
+if ! grep -q "^Driver: docker$"  <<<"${current_builder}" \
+  && grep -q "linux/amd64" <<<"${current_builder}" \
+  && grep -q "linux/arm" <<<"${current_builder}" \
+  && grep -q "linux/arm64" <<<"${current_builder}" \
+  && grep -q "linux/ppc64le" <<<"${current_builder}" \
+  && grep -q "linux/s390x" <<<"${current_builder}"; then
+  exit 0
+fi
+
+# Ensure qemu is in binfmt_misc
+# NOTE: Please always pin this to a digest for predictability/auditability
+# Last updated: 08/21/2020
+if [ "$(uname)" == 'Linux' ]; then
+  docker run --rm --privileged multiarch/qemu-user-static@sha256:c772ee1965aa0be9915ee1b018a0dd92ea361b4fa1bcab5bbc033517749b2af4 --reset -p yes
+fi
+
+# Ensure we use a builder that can leverage it (the default on linux will not)
+docker buildx rm containerd-buildkit-multiarch || true
+docker buildx create --use --name=containerd-buildkit-multiarch
+docker buildx inspect --bootstrap