sisupdate: Allow `readlinkat` syscall

There were crashes found with the recent change in glibc which
requires the `readlinkat` to be permitted.  This commit simply
adds that to the allowlist.

BUG=b:324966703
TEST=deploy touch_updater on shyvana, run update verify that
there are no minijail violations

Change-Id: Ic5f74d19cfb3a735c562832d7f344a777d4868be
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/touch_updater/+/5310232
Tested-by: Aseda Aboagye <aaboagye@chromium.org>
Commit-Queue: Henry Barnor <hbarnor@chromium.org>
Reviewed-by: Henry Barnor <hbarnor@chromium.org>
Auto-Submit: Aseda Aboagye <aaboagye@chromium.org>
2 files changed