Work around issue flavorjones/mini_portile#161

`activate` is actually not needed in cross builds.

Author: larskanis

ext/nokogiri/extconf.rb

@@ -550,7 +550,6 @@ def recipe.port_path
       chdir_for_build { recipe.cook }
       FileUtils.touch(checkpoint)
     end
-    recipe.activate
   end
 end