Be more verbose when we can't clean up a mountpoint
left over from an earlier run.
Include KERNCONF=<kernconf> in /etc/src.conf so that
"make buildkernel" and "make installkernel" will Just Work
on the built system.
Use the new U-Boot-beaglebone port if it's installed.
Merge branch 'skibo-master'
Fix building for qemu
Merge pull request #10 from zxombie/master

Fix building for qemu
Correctly handle failures when we can't install ubldr.