eliminate mac xcode 5 only warning

eliminate mac xcode 5 only warning

on os x 10.9.2 unistd.h defines sysconf as

long	 sysconf(int);

Committed: http://code.google.com/p/skia/source/detail?r=14559

[mtklein, 2014-04-30 20:40:56]

lgtm

[caryclark, 2014-04-30 20:44:33]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2014-04-30 20:44:58]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/caryclark@google.com/261673004/1

[commit-bot: I haz the power, 2014-04-30 20:45:02]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-30 20:45:02]

Presubmit check for 261673004-1 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com')

[reed1, 2014-05-01 16:22:10]

lgtm

[caryclark, 2014-05-01 16:22:23]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2014-05-01 16:22:39]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/caryclark@google.com/261673004/1

[commit-bot: I haz the power, 2014-05-01 19:16:09]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-01 19:16:10]

Retried try job too often on Build-Ubuntu13.10-GCC4.8-Arm7-Debug-Nexus7-Trybot
for step(s) BuildBench, BuildEverything, BuildGm, BuildSkiaLib, BuildTests,
BuildTools
http://skia-tree-status.appspot.com/redirect/compile-buildbots/buildstatus?bu...

[caryclark, 2014-05-04 00:46:31]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2014-05-04 00:46:41]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/caryclark@google.com/261673004/1

[commit-bot: I haz the power, 2014-05-04 00:46:52]

Change committed as 14559