Change default skia_osx_sdkroot to "macosx" (suitable for Xcode 3.2.6+)
See https://codereview.appspot.com/6553044
BUG=https://code.google.com/p/skia/issues/detail?id=796
Review URL: https://codereview.appspot.com/6598055

git-svn-id: http://skia.googlecode.com/svn/trunk@5806 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/common_variables.gypi b/gyp/common_variables.gypi
index bf6d918..d2a3d10 100644
--- a/gyp/common_variables.gypi
+++ b/gyp/common_variables.gypi
@@ -77,7 +77,7 @@
       'android_make_apk%': 1,
       'skia_nacl%': 0,
       'skia_gpu%': 1,
-      'skia_osx_sdkroot%': 'macosx10.6',
+      'skia_osx_sdkroot%': 'macosx',
     },
 
     # Re-define all variables defined within the level-2 'variables' dict,