ensure buildx

[aojea]

Job now fails with https://prow.k8s.io/log?job=post-kindnet-image&id=1978752805577428992

tus: Downloaded newer image for gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:latest
gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:latest
docker buildx build . \
	--progress="auto" \
	--platform="linux/amd64,linux/arm64" \
	--tag="gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20250513-9264efb079" --push
ERROR: Multi-platform build is not supported for the docker driver.
Switch to a different driver, or turn on the containerd image store, and try again.
Learn more at https://docs.docker.com/go/build-multi-platform/
make: *** [Makefile:50: image-push] Error 1
ERROR
ERROR: build step 0 "gcr.io/k8s-staging-test-infra/gcb-docker-gcloud" failed: step exited with non-zero status: 2
--------------------------------------------------------------------------------
2025/10/16 09:22:37 Failed to run some build jobs: [error running [gcloud builds submit --verbosity info --config /home/prow/go/src/github.com/kubernetes-sigs/kindnet/cloudbuild.yaml --substitutions _PULL_BASE_SHA=ce852b3ebd46cbc1803a533f036d7903a9bb133b,_GIT_TAG=v20251016-ce852b3 --project k8s-staging-networking --gcs-log-dir gs://k8s-staging-networking-gcb/logs --gcs-source-staging-dir gs://k8s-staging-networking-gcb/source gs://k8s-staging-networking-gcb/source/74952561-fd48-46b9-94ab-212df32e84db.tgz --polling-interval 10]: exit status 1]
{"component":"entrypoint","error":"wrapped process failed: exit status 1","file":"sigs.k8s.io/prow/pkg/entrypoint/run.go:84","func":"sigs.k8s.io/prow/pkg/entrypoint.Options.internalRun","level":"error","msg":"Error executing test process","severity":"error","time":"2025-10-16T09:22:37Z"}

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aojea

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• OWNERS [aojea]

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[aojea]

/assign @ameukam

[ameukam]

/lgtm