Earlier versions of podman did not make use of TMPDIR when running "podman
run ...". Podman's default, /var/tmp, presents a problem to rootless
use since OpenWrt's /var/tmp does not permit writes by non-root users.
Podman 3.3.1 makes full use of TMPDIR.

This is part of an attempt to get rootless podman to work on OpenWrt.
See https://github.com/openwrt/packages/issues/15096.

See also the upstream issue at
https://github.com/containers/podman/issues/10698.

Signed-off-by: W. Michael Petullo <mike@flyn.org>