Run single downloader
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59278 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Run single downloader
download in single process for each targets, not for each files
in parallel, to get rid of conflicts.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59278 b2dd03c8-39d4-4d8f-98ff-823fe69b080e