To enable, add the following to your .gclient file:

  "custom_vars": {
    "checkout_angle_internal":"True",
  },

Bug: angleproject:3630
Change-Id: I639ba5236fc6d90060a7b50bd0942fe2d0285a25
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1949604
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>