cross build for RELENG8 on RELENG10 now fails

[Doug Ambrisko]

On Wed, Sep 10, 2014 at 11:52:09AM -0400, John Baldwin wrote:
| On Wednesday, September 10, 2014 11:42:14 AM Mike Tancsa wrote:
| > When I upgraded our cross build server to RELENG10 from 9, I lost the
| > ability to build RELENG_8 images.  Is there some magic that needs to be
| > done in order to make this work on RELENG_10 ?
| 
| I punted on building 8 on 10 when I ran into this (I know use bhyve vms 
| running 8 to test MFCs to 8 since I can boot-test them as well as build-test 
| them).  I don't think there are any known workarounds.

We've been building older releases via chroot and setting environment
variables.  I have some local hacks to set the uname etc info. in
a jail via sysctl in the jail.

Doug A.