This completely removes the dependency on glad by generating the GL
headers from gl.xml directly.
This requires adding khrplatform.h so all Khronos dependencies are
gathered in third_party/khronos.
Also removes a stray CMakeLists.txt that was still hanging out.
BUG=dawn:165
Change-Id: Ia64bc51bc8b18c6b48613918e2f309f7405ecb3b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/8163
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Corentin Wallez