crash: change sender to use unique /tmp dir

Now that the runtime/test knobs are in /run and not /tmp, we can
set up a unique /tmp path for this script everytime we run it.

BUG=chromium:766275
TEST=precq passes

Change-Id: I6ae974b2f3c82162fe943168b5b63d725bba5660
Reviewed-on: https://chromium-review.googlesource.com/723869
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
diff --git a/crash-reporter/crash_sender b/crash-reporter/crash_sender
index 57cf5f9..14eca90 100755
--- a/crash-reporter/crash_sender
+++ b/crash-reporter/crash_sender
@@ -758,7 +758,7 @@
   # We use --ambient because crash_sender is a shell script and we run `rm`.
   # We need network access in order to upload things.
   # We don't use -i as the scheduler waits for the first process to exit.
-  exec /sbin/minijail0 -c 0x2 --ambient -n -l -p -r -v --uts -- \
+  exec /sbin/minijail0 -c 0x2 --ambient -n -l -p -r -v -t --uts -- \
     /sbin/crash_sender "$@"
 fi