extconf.rb: VPATH
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37934 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
extconf.rb: VPATH
without copying by using VPATH.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37934 b2dd03c8-39d4-4d8f-98ff-823fe69b080e