... we should probably add a patch to ruby setup.rb to make it respect Gem.disable_system_update_message, i.e., if that's set, show the message and abort the upgrade, just like gem update --system does.

And add some note to documentation about using a version manager rather than an OS packaged version of Ruby for developing RubyGems.

Originally posted by @deivid-rodriguez in #8237 (comment)