Use a custom, world-accessible, /tmp mount

This solves two problems:

1. Using the host /tmp directly meant that concurrent tests could
   collide attempting to use the same file, and that misbehaving tests
   never have their /tmp output cleaned up.
2. Host /tmp is not world-accessible on all hosts. Some tests (e.g.,
   sticky) access files in /tmp from other users, so we need to ensure
   that its /tmp is world-accessible.

PiperOrigin-RevId: 235637873
Change-Id: I7555224685ac5b93af88c403196b09ce1bb2bfe7

0 files changed, 0 insertions, 0 deletions