In some configs these are enabled by default, and they causes linker
warnings (which are treated as errors).

BUG=angleproject:1250

Change-Id: Ia8d28e313c91f1d63248aa5c68d29f9c69b8d596
Reviewed-on: https://chromium-review.googlesource.com/317566
Tryjob-Request: Austin Kinross <aukinros@microsoft.com>
Tested-by: Austin Kinross <aukinros@microsoft.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>