test: skip default gems
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36374 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test: skip default gems
before installation.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36374 b2dd03c8-39d4-4d8f-98ff-823fe69b080e