Merge pull request #9479 from MikeMcQuaid/fix-portable-ruby-cleanup

cleanup: fix portable Ruby behaviour.

Library/Homebrew/brew.sh

@@ -455,6 +455,7 @@ export HOMEBREW_MACOS_VERSION_NUMERIC
 export HOMEBREW_USER_AGENT
 export HOMEBREW_USER_AGENT_CURL
 export HOMEBREW_BOTTLE_DEFAULT_DOMAIN
+export HOMEBREW_MACOS_SYSTEM_RUBY_NEW_ENOUGH
 
 if [[ -n "$HOMEBREW_MACOS" && -x "/usr/bin/xcode-select" ]]
 then

Library/Homebrew/cleanup.rb

@@ -361,6 +361,8 @@ module Homebrew
 
       use_system_ruby = if Homebrew::EnvConfig.force_vendor_ruby?
         false
+      elsif OS.mac?
+        ENV["HOMEBREW_MACOS_SYSTEM_RUBY_NEW_ENOUGH"].present?
       else
         check_ruby_version = HOMEBREW_LIBRARY_PATH/"utils/ruby_check_version_script.rb"
         rubies.uniq.any? do |ruby|