I can see how it may be necessary. I usually run my tests from with local `riak_test` as CWD but every once and a while thats not the case. I ran into the same thing writing some ZSH completions for rt (but used an env var, although i could have parsed out `rt_dir` from the config in hindsight). I don't think requiring the extra config option is a bad thing (we already require hardcoded path for `rt_deps`). Perhaps just updating the readme and example config are good enough?