[OE-core] busybox can no longer upgrade on a running system

[Mike Looijmans]

Don't think anyone noticed yet, but if you try to upgrade busybox 
through "opkg upgrade", you'll end up with a bricked box.

Apparently busybox kills the /bin/sh link somewhere during the upgrade, 
and that results in the upgrade failing and a system that won't boot.

One way to work around the problem appears to be to remove "/bin/sh" 
from the busybox.links.nosuid file, so that update-alternatives won't 
touch it.

I haven't figured out yet what caused the regression. It's probably been 
like this for months.

-- 
Mike Looijmans