fix: build on sierra

mac/find_sdk.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Prints the lowest locally available SDK version greater than or equal to a
 given minimum sdk version to standard output. If --developer_dir is passed, then
 the script will use the Xcode toolchain located at DEVELOPER_DIR.
 
 Usage:
@@ skipping 35 matching lines @@
 
   job = subprocess.Popen(['xcode-select', '-print-path'],
                          stdout=subprocess.PIPE,
                          stderr=subprocess.STDOUT)
   out, err = job.communicate()
   if job.returncode != 0:
     print >> sys.stderr, out
     print >> sys.stderr, err
     raise Exception('Error %d running xcode-select' % job.returncode)
   sdk_dir = os.path.join(
-      out.rstrip(), 'Platforms/MacOSX.platform/Developer/SDKs')
+      out.rstrip(), 'SDKs')
   sdks = [re.findall('^MacOSX(10\.\d+)\.sdk$', s) for s in os.listdir(sdk_dir)]
   sdks = [s[0] for s in sdks if s]  # [['10.5'], ['10.6']] => ['10.5', '10.6']
   sdks = [s for s in sdks  # ['10.5', '10.6'] => ['10.6']
           if parse_version(s) >= parse_version(min_sdk_version)]
   if not sdks:
     raise Exception('No %s+ SDK found' % min_sdk_version)
   best_sdk = sorted(sdks, key=parse_version)[0]
 
   if options.verify and best_sdk != min_sdk_version and not options.sdk_path:
     print >> sys.stderr, ''
@@ skipping 14 matching lines @@
         ['xcrun', '-sdk', 'macosx' + best_sdk, '--show-sdk-path']).strip()
 
   return best_sdk
 
 
 if __name__ == '__main__':
   if sys.platform != 'darwin':
     raise Exception("This script only runs on Mac")
   print main()
   sys.exit(0)