http://lists.xenproject.org/archives/html/xen-users/2016-03/msg00092.html
I saw this post to xen-users. My mail client has not yet received it, so I
replied in a non-standard way.
I have had similar or same issues as you, and more, compiling this. You
will have other problems running Xen on Xenial, especially if your domU are
LVM based.
Here is my effort:
http://107.185.144.55/xen/ubuntu/xenial/46x/
I like building from the tarball, since its easier to patch (from xen root
base). Also the release tarball has qemu included. My linked build folder
also has a binary for ovmf.bin.46
If you wonder why building on Xenial is so chaotic, its because the Xen
devs/testers do not support gcc 5.x and have no interest. They only
recently started running Deb 8.x tests on their OSSTEST system.
PryMar56 on #xen