make.sh: Suppress 'ls :cannot access *.bz2'-message

make.sh: Suppress 'ls :cannot access *.bz2'-message

The message "ls: cannot access '*.bz2': No such file or directory" comes
from the 'ls' command prior to creating the *.md5-files for *.bz2, *.img.xz
and *.iso files.

But on most builds we have especially no more bzip2 compressed images anymore.

This message can usually be ignored and is just irritating.

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>