Do not force Xcode clang when targetting arm64

Do not force Xcode clang when targetting arm64

ToT clang now supports building for arm64 so remove the exception forcing
using Xcode clang when targeting arm64 (or fat binaries) on iOS.

BUG=341453
Committed: https://crrev.com/d4eb6e6969630f51fb64478e1f863591220d292c
Cr-Commit-Position: refs/heads/master@{#316549}

[sdefresne, 2015-02-16 18:21:04]

sdefresne@chromium.org changed reviewers:
+ thakis@chromium.org

[sdefresne, 2015-02-16 18:21:04]

I can now successfully build 64-bit binaries for iOS using ToT clang, so I think
this override is no longer necessary.

Please take a look.

[Nico, 2015-02-16 20:26:15]

On 2015/02/16 18:21:04, sdefresne wrote:
> I can now successfully build 64-bit binaries for iOS using ToT clang, so I
think
> this override is no longer necessary.
> 
> Please take a look.

Lgtm

(I still think it's weird that the compiler depends on which generator is used,
BTW)

[sdefresne, 2015-02-17 09:51:51]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2015-02-17 09:52:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/932673002/1

[commit-bot: I haz the power, 2015-02-17 09:55:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-17 09:56:35]

Patchset 1 (id:??) landed as
https://crrev.com/d4eb6e6969630f51fb64478e1f863591220d292c
Cr-Commit-Position: refs/heads/master@{#316549}