tests: Import the googletest library, release version 1.8.0.

Change-Id: Ic6c1391a19238011ff5cc97f513dbdc020dc6144
Reviewed-on: https://gem5-review.googlesource.com/6082
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
200 files changed