This could avoid including dawn's version of webgpu headers
and confusion at runtime when build with emscripten.
Emscripten's system/include/webgpu headers should be used.
Bug: None
Change-Id: Ie8c6ebc23f28a56b1cb887ae7f11d3f738151aec
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/79740
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Shrek Shao <shrekshao@google.com>