Ruby » Ruby master

extmk.rb: fix gem target directory name

• ext/extmk.rb: make the gems target directory under the expanded
  name. [ruby-core:77102] [Bug #12714]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56042 b2dd03c8-39d4-4d8f-98ff-823fe69b080e