def _GaeBuilderPackagePath(runtime):
  """GCR package path for a builder that works on the given appengine runtime.

  Args:
    runtime: Name of a runtime from app.yaml, e.g. 'python38'.

  Returns:
    gcr.io image path.
  """
  return 'gcr.io/gae-runtimes/buildpacks/%s/builder:latest' % runtime