This flag is not supported on mac and generates errors when trying to
roll.

BUG=b:150892231

Change-Id: I22d10a2b9b37610d409df4d72e0aba2672f7b192
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2152666Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Geoff Lang <geofflang@chromium.org>