Translator headers that are included by dependent code
(example: ShaderLang.h) expect to be able to include files from
"includes" (example: "KHR/khrplatform.h"). This automatically
applies this include path to dependent targets.

Change-Id: I6990f66132562f142a6cdf8b8c434d2dbaad1c98
Reviewed-on: https://chromium-review.googlesource.com/209452Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Brett Wilson <brettw@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>