Currently, the mongosync project relies on passing in the --configDir parameter when executing the evergreen_gen_build_variant.py script. However, it ends up overwriting the passed in config options with the defaults because it ends up calling set_run_options (called by ResmokeProxy) twice:

1. Initially, evergreen_gen_build_variant will set the proper resmoke configs here
2. But then MultiversionDecorator will overwrite those options when creating another ResmokeProxy here without any arguments