Automatically determine the gcc compiler to use based on XCode version

tools/gyp/find_mac_gcc_version.py

+#!/usr/bin/env python
+# Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import re
+import subprocess
+import sys
+
+def main():
+  job = subprocess.Popen(['xcodebuild', '-version'],
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.STDOUT)
+  stdout, stderr = job.communicate()
+  if job.returncode != 0:
+    print >>sys.stderr, stdout
+    print >>sys.stderr, stderr
+    raise Exception('Error %d running xcodebuild!' % job.returncode)
+  matches = re.findall('^Xcode (\d+)\.(\d+)\.(\d+)$', stdout, re.MULTILINE)
+  if len(matches) > 0:
+    major = int(matches[0][0])
+    minor = int(matches[0][1])
+
+    if major >= 4:
+      return 'com.apple.compilers.llvmgcc42'
+    elif major == 3 and minor >= 1:
+      return '4.2'
+    else:
+      raise Exception('Unknown XCode Version "%s"' % version_match)
+  else:
+    raise Exception('Could not parse output of xcodebuild "%s"' % stdout)
+
+if __name__ == '__main__':
+  if sys.platform != 'darwin':
+    raise Exception("This script only runs on Mac")
+  print main()