If you remove the MONGO_INITIALIZER block for the copyDB command in s/commands_public.cpp and recompile mongos with the enterprise module linked in, then run mongos, it immediately crashes on startup saying:

> ./mongos --configdb localhost
Mon Apr  1 15:05:35.010 warning: running with 1 config server should be done only for testing purposes and is not recommended for production
Failed global initialization: AlreadyInitialized gcrypt library already initialized

Putting the MONGO_INITIALIZER block back in fixes the problem, as does compiling without the enterprise module.