test_io.rb: skip writev test
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60424 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_io.rb: skip writev test
needs writev which is not portable. [Feature #14042]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60424 b2dd03c8-39d4-4d8f-98ff-823fe69b080e