Get the proper Mac SDK path for the GN build.

build/mac/find_sdk.py

Index: build/mac/find_sdk.py
diff --git a/build/mac/find_sdk.py b/build/mac/find_sdk.py
index 067be638d21c55b083780e2a57b9034508f3486b..1d7634391fa4d66b2baeec276429836c39d53283 100755
--- a/build/mac/find_sdk.py
+++ b/build/mac/find_sdk.py
@@ -31,6 +31,9 @@ def main():
   parser.add_option("--sdk_path",
                     action="store", type="string", dest="sdk_path", default="",
                     help="user-specified SDK path; bypasses verification")
+  parser.add_option("--print_sdk_path",
+                    action="store_true", dest="print_sdk_path", default=False,
+                    help="Additionaly print the path the SDK (appears first).")
   (options, args) = parser.parse_args()
   min_sdk_version = args[0]
 
@@ -73,6 +76,10 @@ def main():
     print >>sys.stderr, ''
     return min_sdk_version
 
+  if options.print_sdk_path:
+    print subprocess.check_output(['xcodebuild', '-version', '-sdk',
+                                   'macosx' + best_sdk, 'Path']).strip()
+
   return best_sdk