Update Xcode or Homebrew (apply https://github.com/nobu/ruby/commit/c86b74dc431d4cbdeb7d3c3fe5ac0693dc731bb1) [Bug #16032]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67730 b2dd03c8-39d4-4d8f-98ff-823fe69b080e