Don't install bundled gems - we package them separately.

--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -947,6 +947,7 @@
   end
 end
 
+=begin XXX-Patched
 install?(:ext, :comm, :gem, :'bundled-gems') do
   gem_dir = Gem.default_dir
   install_dir = with_destdir(gem_dir)
@@ -1026,6 +1027,7 @@
     puts "skip installing bundled gems because of lacking zlib"
   end
 end
+=end
 
 parse_args()