Test trigger of cloudbuild for nginx image

hack/init-buildx.sh

@@ -24,6 +24,11 @@ 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)"

images/nginx/cloudbuild.yaml

@@ -4,13 +4,16 @@ options:
   # job builds a multi-arch docker image for amd64,arm,arm64 and s390x.
   machineType: N1_HIGHCPU_32
 steps:
-  - name: gcr.io/k8s-testimages/gcb-docker-gcloud:v20200422-b25d964
+  - name: gcr.io/k8s-testimages/gcb-docker-gcloud:v20200619-68869a4
     entrypoint: bash
     env:
       - DOCKER_CLI_EXPERIMENTAL=enabled
       - TAG=$_GIT_TAG
       - BASE_REF=$_PULL_BASE_REF
       - REGISTRY=gcr.io/k8s-staging-ingress-nginx
+      # default cloudbuild has HOME=/builder/home and docker buildx is in /root/.docker/cli-plugins/docker-buildx
+      # set the home to /root explicitly to if using docker buildx
+      - HOME=/root
     args:
     - -c
     - |