Improve buildx configuration

hack/init-buildx.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+
+# 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.
+
+if [ -n "$DEBUG" ]; then
+	set -x
+fi
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+export DOCKER_CLI_EXPERIMENTAL=enabled
+
+if ! docker buildx 2>&1 >/dev/null; then
+  echo "buildx not available. Docker 19.03 or higher is required with experimental features enabled"
+  exit 1
+fi
+
+# We can skip setup if the current builder already has multi-arch
+# AND if it isn't the docker driver, which doesn't work
+current_builder="$(docker buildx inspect)"
+# linux/amd64, linux/arm64, linux/riscv64, linux/ppc64le, linux/s390x, linux/386, linux/arm/v7, linux/arm/v6
+if ! grep -q "^Driver: docker$"  <<<"${current_builder}" && \
+     grep -q "linux/amd64" <<<"${current_builder}" && \
+     grep -q "linux/arm"   <<<"${current_builder}" && \
+     grep -q "linux/arm64" <<<"${current_builder}" && \
+     grep -q "linux/s390x" <<<"${current_builder}"; then
+  exit 0
+fi
+
+# Ensure qemu is in binfmt_misc
+# Docker desktop already has these in versions recent enough to have buildx
+# We only need to do this setup on linux hosts
+if [ "$(uname)" == 'Linux' ]; then
+  # NOTE: this is pinned to a digest for a reason!
+  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 ingress-nginx || true
+docker buildx create --use --name=ingress-nginx