Add osx support

python/servo/bootstrapper/bootstrap.py

@@ -9,6 +9,7 @@
 
 from centosfedora import CentOSFedoraBootstrapper
 from debian import DebianBootstrapper
+from osx import OSXBootstrapper
 from windows_gnu import WindowsGnuBootstrapper
 from windows_msvc import WindowsMsvcBootstrapper
 
@@ -51,6 +52,12 @@ def __init__(self):
             args['version'] = version
             args['dist_id'] = dist_id
 
+        elif sys.platform.startswith('darwin'):
+            osx_version = platform.mac_ver()[0]
+
+            cls = OSXBootstrapper
+            args['version'] = osx_version
+
         elif sys.platform.startswith('msys'):
             cls = WindowsGnuBootstrapper