gyp: Remove the post-build script hook. This was used by developers to copy compiled libs around. With better dEQP integration and supporting tools it is no longer necessary. BUG=None Change-Id: Iff35be88111c2c806bb02abf43ffb33ed5b641fd Reviewed-on: https://chromium-review.googlesource.com/340589 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>