Revert of update.py: Check out and build libc++ libc++abi on OS X, set deployment target.

Revert of update.py: Check out and build libc++ libc++abi on OS X, set deployment target. (patchset #3 id:40001 of https://codereview.chromium.org/1169353002/)

Reason for revert:
broke clang/win tot bots

Original issue's description:
> update.py: Check out and build libc++ libc++abi on OS X, set deployment target.
>
> I had hoped to bump the deployment target to 10.7 instead, but the nacl bots
> still build on 10.6 :-(
>
> Also, pass commands as a single string to subprocess when
> shell=True (else, 2nd cmd entry and onward are treated as
> shell parameters, not as part of the command).
>
> BUG=494442
>
> Committed: https://crrev.com/8fe06c48bbe07670dba3cafdd4c613f0008948f9
> Cr-Commit-Position: refs/heads/master@{#333669}

TBR=hans@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=494442
Committed: https://crrev.com/6a120cded321773b6851e566470c3bd08c7bb714
Cr-Commit-Position: refs/heads/master@{#333737}

[Nico, 2015-06-10 15:27:04]

Created Revert of update.py: Check out and build libc++ libc++abi on OS X, set
deployment target.

[commit-bot: I haz the power, 2015-06-10 15:27:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1172363002/1

[commit-bot: I haz the power, 2015-06-10 15:28:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-10 15:29:13]

Patchset 1 (id:??) landed as
https://crrev.com/6a120cded321773b6851e566470c3bd08c7bb714
Cr-Commit-Position: refs/heads/master@{#333737}