Some tweaks to when we call gtest initialization allows this to work.

Bug: angleproject:3162
Change-Id: I75159108d3f746f666e57c1a6495a8c8616ef1cf
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2024335
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>