Make use_goma=true also work for Mac GN.

Make use_goma=true also work for Mac GN.

Since toolchain/mac/BUILD.gn did not have anything to support
use_goma, even if use_goma=true set, the flags was just ignored.

BUG=459435
Committed: https://crrev.com/874b8fe5991b4f57088f3ff4218cc8e8acd2b18d
Cr-Commit-Position: refs/heads/master@{#316758}

[Yoshisato Yanagisawa, 2015-02-18 02:45:50]

yyanagisawa@chromium.org changed reviewers:
+ brettw@chromium.org, scottmg@chromium.org, thakis@chromium.org

[Yoshisato Yanagisawa, 2015-02-18 02:45:50]

Hi,

I found gn --args=use_goma=true is ignored on mac build.
Let me make use_goma also work on mac.

[Nico, 2015-02-18 02:54:23]

lgtm

[scottmg, 2015-02-18 02:55:16]

The linux one uses compiler_prefix, rather than goma_prefix. Maybe would be
better to be consistent, but lgtm either way.

[Yoshisato Yanagisawa, 2015-02-18 02:55:20]

The CQ bit was checked by yyanagisawa@chromium.org

[Dirk Pranke, 2015-02-18 02:55:35]

dpranke@chromium.org changed reviewers:
+ dpranke@chromium.org

[Dirk Pranke, 2015-02-18 02:55:35]

that might explain a few things ... :).

lgtm also.

[Yoshisato Yanagisawa, 2015-02-18 02:55:36]

The CQ bit was unchecked by yyanagisawa@chromium.org

[Yoshisato Yanagisawa, 2015-02-18 03:00:06]

I saw both linux/BUILD.gn and win/BUILD.gn.  Linux uses compiler_prefix and
Windows uses goma_prefix.  Since I did not see ccache code in mac, I followed
the way of Windows.
Let me submit this as-is.

[Yoshisato Yanagisawa, 2015-02-18 03:00:08]

The CQ bit was checked by yyanagisawa@chromium.org

[commit-bot: I haz the power, 2015-02-18 03:00:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/932013004/1

[commit-bot: I haz the power, 2015-02-18 03:18:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-18 03:19:56]

Patchset 1 (id:??) landed as
https://crrev.com/874b8fe5991b4f57088f3ff4218cc8e8acd2b18d
Cr-Commit-Position: refs/heads/master@{#316758}