A few symlinks were pointing to a nonexistent file named '(null)'
instead of their intended target. This was only seen when using the
arm_sdimage.sh script.
There is two ways of specifying links and directories. the first one
using an entry in one of the mtree files, and the second one in
/etc/Makefile.
Those entries where doubled, and one of them would specify some rights,
while the other had the target.
By removing those entries, I make sure there is only one definition of
these symlinks, which solves the problem I was seeing on an ARM image.
These symlinks are still present on a generated system, as they are
required.