lorgnette: add writeable /tmp to minijail

Some SANE drivers expect a writeable /tmp to create and write
temporary files in.

BUG=b:496201239
TEST=manual test on brya device

Change-Id: I1ed9a46bc3b844bfedfc8899f8b072ec9dd6ed5e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/7802623
Tested-by: Paul Moy <pmoy@chromium.org>
Reviewed-by: Benjamin Gordon <bmgordon@chromium.org>
Commit-Queue: Paul Moy <pmoy@chromium.org>

lorgnette/minijail/lorgnette.conf

diff --git a/lorgnette/minijail/lorgnette.conf b/lorgnette/minijail/lorgnette.conf
index 5f17a12..c7e01df 100644
--- a/lorgnette/minijail/lorgnette.conf
+++ b/lorgnette/minijail/lorgnette.conf
@@ -10,6 +10,7 @@
 N
 p
 r
+t
 ns-mount
 uts
 mount-dev