This should significantly speed up checkout on dev machines.

Bug: angleproject:5133
Change-Id: Iba20182c600ea8e17de47bb4e84b2e4191d301d3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2527721Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>