Set mac_deployment_target default to 10.7

Set mac_deployment_target default to 10.7

This overrides the default (10.6) in Chromium's
build/common.gypi. It's needed since we want ARC and libc++.

TESTED=Ran webrtc/build/gyp_webrtc before this patch and then
grep -r macosx-version-min out/Debug/* | grep 10.6
which gave a lot of output.
Then with this patch applied, there were no output for 10.6 (only 10.7).

R=tkchin@webrtc.org

Committed: https://chromium.googlesource.com/external/webrtc/+/46a491bcbb887c7019cbd87cc85429703a69c387

[kjellander_webrtc, 2015-11-24 06:58:37]

Description was changed from

==========
Set mac_deployment_target default to 10.7

This overrides the default (10.6) in Chromium's
build/common.gypi. It's needed since we want ARC and libc++.
==========

to

==========
Set mac_deployment_target default to 10.7

This overrides the default (10.6) in Chromium's
build/common.gypi. It's needed since we want ARC and libc++.

TESTED=Ran webrtc/build/gyp_webrtc before this patch and then
grep -r macosx-version-min out/Debug/* | grep 10.6
which gave a lot of output.
Then with this patch applied, there were no output for 10.6 (only 10.7).
==========

[kjellander_webrtc, 2015-11-24 06:58:38]

kjellander@webrtc.org changed reviewers:
+ tkchin@webrtc.org

[tkchin_webrtc, 2015-11-24 22:55:19]

On 2015/11/24 06:58:38, kjellander (webrtc) wrote:
> mailto:kjellander@webrtc.org changed reviewers:
> + mailto:tkchin@webrtc.org

lgtm
just for my own understanding - this only affects standalone right? So chromium
builds won't be affected by this?

[kjellander_webrtc, 2015-11-25 07:29:11]

On 2015/11/24 22:55:19, tkchin_webrtc wrote:
> On 2015/11/24 06:58:38, kjellander (webrtc) wrote:
> > mailto:kjellander@webrtc.org changed reviewers:
> > + mailto:tkchin@webrtc.org
> 
> lgtm
> just for my own understanding - this only affects standalone right? So
chromium
> builds won't be affected by this?

Right, this won't affect Chromium as long as their defaults in
https://code.google.com/p/chromium/codesearch#chromium/src/build/common.gypi are
lower than what we have here, so we have to pay attention to when that changes.
It should take a long time though, since they seem very conservative about that.

[commit-bot: I haz the power, 2015-11-25 07:35:14]

Patchset 3 (id:??) landed as
https://crrev.com/46a491bcbb887c7019cbd87cc85429703a69c387
Cr-Commit-Position: refs/heads/master@{#10783}

[kjellander (google.com), 2015-11-25 07:35:16]

Committed patchset #3 (id:40001) manually as
46a491bcbb887c7019cbd87cc85429703a69c387.