Adding option to create XCode project

Change-Id: I4d5792ff3bc3f8cc169ad3af3f7924344f55855c
diff --git a/wscript b/wscript
index 54b83ac..6bbd913 100644
--- a/wscript
+++ b/wscript
@@ -6,7 +6,7 @@
 
 def options(opt):
     opt.load('compiler_c compiler_cxx')
-    opt.load('sparkle', tooldir='waf-tools')
+    opt.load('sparkle xcode', tooldir='waf-tools')
 
 def configure(conf):
     conf.load('compiler_c compiler_cxx')