In a cluster build, eMake will attempt to secure its connections with agents according to a mode set by the first of the following that exists:
--emake-agent-security=… command line option
EMAKE_AGENT_SECURITY environment variable
If none of the above specifies the mode, then eMake defaults to unauthenticated communications with agents. But if one of the above specifies an unrecognized mode, then eMake fails with EC1171.