Add macOS support to update_chrome_angle.py Bug: angleproject:1944 Change-Id: I3e2503b462df82ffa2bef3814b1979448dee09e9 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3358242 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com>