Set WITH_SYSTEM_CALLS to none by default

DefineOptions.cmake

@@ -22,7 +22,7 @@ if (NUM_HEAPS GREATER 1)
   set(MULTIPLE_HEAPS ON)
 endif (NUM_HEAPS GREATER 1)
 
-set(WITH_SYSTEM_CALLS "no")
+set(WITH_SYSTEM_CALLS "none")
 
 set(SEARCH_POLICY "best")
 set(FIT_PERCENTAGE 0.8)