rbinstall.rb: CONFIG['arch'] not $arch
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39131 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
rbinstall.rb: CONFIG['arch'] not $arch
added finally. fix r39108.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39131 b2dd03c8-39d4-4d8f-98ff-823fe69b080e