Build arm64 as well

Signed-off-by: Pete Wall <pete.wall@grafana.com>

Author: petewall

.github/workflows/build-kubectl.yaml

@@ -47,7 +47,7 @@ jobs:
         uses: docker/build-push-action@d08e5c354a6adb9ed34480a06d141179aa583294  # v7.0.0
         with:
           context: tools/kubectl-image
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
           provenance: false
           sbom: false
           push: true