build: create GCB test that ensures the image builds (#3517)
build: create GCB test that ensures the image builds (#3517)

Future PRs touching the serverless-scheduler-proxy directory will trigger this build as a presubmit

googleapis/repo-automation-bots,googleapis/repo-automation-bots,googleapis/repo-automation-bots,googleapis/repo-automation-bots,googleapis/repo-automation-bots