Use system Xcode on Mac instead of the hermetic toolchain.

Use system Xcode on Mac instead of the hermetic toolchain.

WebRTC needs the 10.12 SDK to compile successfully, which is
not availble in the hermetic toolchain Chromium is rolling out
to Googlers.
This CL depends on https://codereview.chromium.org/2494103002/
being landed and rolled into WebRTC first.

BUG=webrtc:6700

[kjellander_webrtc, 2016-11-14 07:12:57]

This is replaced by https://codereview.webrtc.org/2496113002

[kjellander_webrtc, 2016-11-14 07:13:02]

Description was changed from

==========
Use system Xcode on Mac instead of the hermetic toolchain.

WebRTC needs the 10.12 SDK to compile successfully, which is
not availble in the hermetic toolchain Chromium is rolling out
to Googlers.
This CL depends on https://codereview.chromium.org/2494103002/
being landed and rolled into WebRTC first.

BUG=webrtc:6700
==========

to

==========
Use system Xcode on Mac instead of the hermetic toolchain.

WebRTC needs the 10.12 SDK to compile successfully, which is
not availble in the hermetic toolchain Chromium is rolling out
to Googlers.
This CL depends on https://codereview.chromium.org/2494103002/
being landed and rolled into WebRTC first.

BUG=webrtc:6700
==========