mac: Print an error when doing a branded build and the 10.6 sdk is not around

mac: Print an error when doing a branded build and the 10.6 sdk is not around

BUG=144045
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=152823

[Mark Mentovai, 2012-08-22 13:08:57]

I’m not sure if the Xcode 3-running (official) bots will like this. Have you
tested this with Xcode 3?

[Nico, 2012-08-22 15:14:18]

It was missing a somewhat important bit. With that bit (patch set 2), it seems
to work on my 10.6 box.

[Mark Mentovai, 2012-08-22 15:39:38]

LGTM

[commit-bot: I haz the power, 2012-08-22 15:48:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/10876003/4001

[commit-bot: I haz the power, 2012-08-22 17:25:39]

Try job failure for 10876003-4001 (retry) on win for step "compile" (clobber
build).
It's a second try, previously, step "compile" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win&number...

[commit-bot: I haz the power, 2012-08-22 17:38:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/10876003/4001

[commit-bot: I haz the power, 2012-08-22 19:03:52]

Try job failure for 10876003-4001 (retry) on win for step "compile" (clobber
build).
It's a second try, previously, step "compile" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win&number...