[osx] Fix double colon in /Users/marcin.kumorek/.rvm/gems/ruby-2.2.0/bin:/Users/marcin.kumorek/.rvm/gems/ruby-2.2.0@global/bin:/Users/marcin.kumorek/.rvm/rubies/ruby-2.2.0/bin:/Users/marcin.kumorek/.rvm/bin:/usr/local/bin:/usr/local/sbin:/Users/marcin.kumorek/.nvm/v0.10.33/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/Users/marcin.kumorek/bin