add an option to choose mac sdk for the tools/builds.py

tools/build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2011, 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 optparse
 import os
 import shutil
@@ skipping 18 matching lines @@
       help='Target architectures (comma-separated).',
       metavar='[all,ia32,x64,simarm,arm]',
       default=utils.GuessArchitecture())
   result.add_option("-j",
       help='The number of parallel jobs to run.',
       metavar=HOST_CPUS,
       default=str(HOST_CPUS))
   result.add_option("--devenv",
       help='Path containing devenv.com on Windows',
       default='C:\\Program Files (x86)\\Microsoft Visual Studio 9.0\\Common7\\IDE')
+  result.add_option("--macsdk",
+      help='MacOSX SDK version',
+      metavar='[10.5,10.6,10.7]',
+      default='10.5')
   return result
 
 
 def ProcessOptions(options):
   if options.arch == 'all':
     options.arch = 'ia32,x64'
   if options.mode == 'all':
     options.mode = 'release,debug'
   options.mode = options.mode.split(',')
   options.arch = options.arch.split(',')
@@ skipping 52 matching lines @@
   for mode in options.mode:
     for arch in options.arch:
       build_config = utils.GetBuildConf(mode, arch)
       if HOST_OS == 'macos':
         project_file = 'dart.xcodeproj'
         if os.path.exists('dart-%s.gyp' % CurrentDirectoryBaseName()):
           project_file = 'dart-%s.xcodeproj' % CurrentDirectoryBaseName()
         args = ['xcodebuild',
                 '-project',
                 project_file,
+                '-sdk',
+                'macosx%s'%options.macsdk,
                 '-target',
                 target,
                 '-parallelizeTargets',
                 '-configuration',
                 build_config,
                 'SYMROOT=%s' % os.path.abspath('xcodebuild')
                 ]
       elif HOST_OS == 'win32':
         project_file = 'dart.sln'
         if os.path.exists('dart-%s.gyp' % CurrentDirectoryBaseName()):
@@ skipping 39 matching lines @@
       process.wait()
       if process.returncode != 0:
         print "BUILD FAILED"
         return 1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())