Also adds a script that runs iwyu to the tools_webrtc directory.
Bug: webrtc:11995
Change-Id: I2185a9957e3578c2ec6d0d306061a48fcfe840d4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/188800
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32431}