Usage: trigger.py <GN path> <test> <os_dim> <gpu_dim> <-s shards>

This script can circumvent the trybots when attempting a job on a
specific configuration. It must be used within a Chromium checkout
currently. In the future we can likely use it in standalone.

Optional arguments can specify the number of swarming shards, the pool,
and extra command line test parameters like --gtest_filter.

Bug: angleproject:3272
Change-Id: Ia79f4422786c463378fc7e0f7f5ae4d07bd097a0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1524700
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>