I have High Sierra Beta 6 Installed on my Mac Pro.
High sierra beta comes with Ruby 2.2 and brew doctor
complains about it since it was tested only with ruby 2.0.
I can install ruby 2.0 with homebrew, is there a way to tell homebrew to actually use that version instead of the ruby version that comes with the OS ?
There’s no way to do that. High Sierra is still in beta so it’s normal it’s not fully supported by Homebrew.