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

--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -1003,6 +1003,7 @@
   end
 end
 
+=begin XXX-Patched
 install?(:ext, :comm, :gem, :'bundled-gems') do
   if CONFIG['CROSS_COMPILING'] == 'yes'
     # The following hacky steps set "$ruby = BASERUBY" in tool/fake.rb
@@ -1104,6 +1105,7 @@
     puts "skip installing bundled gems because of lacking zlib"
   end
 end
+=end
 
 parse_args()