Compress subunit tmpfile artifacts on static.o.o.

Change-Id: I8772eefafe7807ac110154f24bcd4959249249c3
Reviewed-on: https://review.openstack.org/24654
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins