This path was broken for the white box unit tests. Also adds argparse
handling to the runner so we can more flexibly override command line
arguments.

Previously the broken calibration was causing some of the tests to run
only a single test iteration when measuring. This could lead to low
quality measurements.

Bug: angleproject:5573
Change-Id: Ic1cb2b2553774a361325f290440c40b2ff90db5e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2672702
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>