Icedtea 1.13.11 was released, which fixes a number of security bugs:

http://blog.fuseyism.com/index.php/2016/05/04/security-icedtea-1-13-11-for-openjdk-6-released/

I tried to build it with the attached patch, but it fails for me. I've
attached the tail of the build log. Any advice?