crosdns: Harden upstart script against symlink attacks.

This installs the tmpfiles.d scripts used to harden the crosdns upstart
script against symlink attacks.

BUG=b:219073235
TEST=verify crosdns starts

Cq-Depend: chromium:3473536
Change-Id: If03880a28094d64729ed78ca5cda7a1371694cfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/3473538
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Allen Webb <allenwebb@google.com>
2 files changed