Update the destination directory's mtime with each backup.

After rsync, the destination directory's mtime reflects the
modification time of its immediate contents.  This patch overrides
that and sets the mtime to the time that the backup finished.

With this patch, the age of a backup can be assessed by looking at
its mtime.  The advantages of this are (1) that mtime can be
preserved, via cp -a or rsync -a, when copying a backup repository
to a new hard disk or a new machine and (2) that incorrect mtimes,
such as might happen after a user meddles with his backup
repository, can be, via touch, corrected.  The disadvantage is that
mtime for the immediate contents of the destination directory is
lost.

ccollect.sh

@@ -536,6 +536,11 @@ while [ "${i}" -lt "${no_sources}" ]; do
    rsync "$@" "${source}" "${destination_full}"; ret=$?
    _techo "Finished backup (rsync return code: $ret)."
 
+   #
+   # Set modification time (mtime) to current time
+   #
+   pcmd touch "${destination_dir}"
+
    #
    # Check if rsync exit code indicates failure.
    #