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

ChangeLog

@@ -1,3 +1,8 @@
+Wed Aug 31 00:52:23 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/extmk.rb: make the gems target directory under the expanded
+	  name.  [ruby-core:77102] [Bug #12714]
+
 Tue Aug 30 15:27:27 2016  Kouhei Yanagita  <yanagi@shakenbu.org>
 
 	* ext/json/lib/json/add/ostruct.rb (OpenStruct.json_create):

ext/extmk.rb

@@ -535,7 +535,7 @@ end
 if $extout
   extout = RbConfig.expand("#{$extout}", RbConfig::CONFIG.merge("topdir"=>$topdir))
   unless $ignore
-    FileUtils.mkpath(extout)
+    FileUtils.mkpath("#{extout}/gems")
   end
 end
 
@@ -565,7 +565,6 @@ end
 
 Dir.chdir('..')
 FileUtils::makedirs('gems')
-FileUtils::makedirs("#$extout/gems")
 Dir.chdir('gems')
 extout = $extout
 gems.each do |d|