Comment 13 for bug 1851091

I was able to find the Xen changes which fix the decoding matter. Right now there is also work needed to work around issues when compiling with gcc-8 (and gcc-9). I got the compiling side fixed, too. Unfortunately the result, when compiling with gcc-9, is a non-working hypervisor. In my tests that just triggers a host reset before even printing any early boot messages. So right now there is only one way of getting an at least working solution for Eoan/Focal: to upload into Disco and copy-forward that (with binaries) to E/F.