This is will help avoid adding many include directories for the GN
build.

BUG=angleproject:929

Change-Id: If8f7e98526df3560b8e410ec86271a2da0c6889d
Reviewed-on: https://chromium-review.googlesource.com/296480Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>