code: func (b *BuildArgs) IsReferencedOrNotBuiltin(key string) bool {
  	_, isBuiltin := builtinAllowedBuildArgs[key]
  	_, isAllowed := b.allowedBuildArgs[key]
  	return isAllowed || !isBuiltin
  }
docs: // IsReferencedOrNotBuiltin checks if the key is a built-in arg, or if it has been
  // referenced by the Dockerfile. Returns true if the arg is not a builtin or
  // if the builtin has been referenced in the Dockerfile.