mac: Let mac_sdk default to the oldest available SDK that's at least 10.6

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
new file mode 100644
index 0000000000000000000000000000000000000000..cbc36d3bee930c381385c40855e56404b3421c52
--- /dev/null
+++ b/build/mac/find_sdk.py
@@ -0,0 +1,53 @@
+#!/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.
+
+import os
+import re
+import subprocess
+import sys
+
+"""Prints the lowest locally available SDK version greater than or equal to a
+given minimum sdk version to standard output.
+
+Usage:
+  python find_sdk.py 10.6  # Ignores SDKs < 10.6
+"""
+
+def parse_version(version_str):
+  """'10.6' => [10, 6]"""
+  return map(int, re.findall(r'(\d+)', version_str))
+
+
+def main(min_sdk_version):
+  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, you might have to run '
+      '|sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer| '
+      'if you are using Xcode 4.') % job.returncode)
+  # The Developer folder moved in Xcode 4.3.
+  xcode43_sdk_path = os.path.join(
+      out.rstrip(), 'Platforms/MacOSX.platform/Developer/SDKs')
+  if os.path.isdir(xcode43_sdk_path):
+    sdk_dir = xcode43_sdk_path
+  else:
+    sdk_dir = os.path.join(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)
+  print sorted(sdks, key=parse_version)[0]
+
+
+if __name__ == '__main__':
+  if sys.platform != 'darwin':
+    raise Exception("This script only runs on Mac")
+  main(min_sdk_version=sys.argv[1])