Formalize preference for handling generated code. This documents the discussion and conclusion on preferring to bake generated code into the repository. Bug: angleproject:3333 Change-Id: I1afc338c59d5bcb2a64f843081aba5120820e9ba Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1558676 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>