Use proptools.CloneEmptyProperties

CloneEmptyProperties is much faster than CloneProperties followed
by ZeroProperties.  Cuts >100ms off soong_build runtime, which will
become more important when we start calling soong_build a second
time to automatically generate documentation.

Change-Id: I45d948b36d9937a21b13dab068c3ce9a60b5a59b

common/arch.go

@@ -377,8 +377,7 @@ func InitArchModule(m AndroidModule, defaultMultilib Multilib,
 
 		archProperties := &archProperties{}
 		forEachInterface(reflect.ValueOf(archProperties), func(v reflect.Value) {
-			newValue := proptools.CloneProperties(propertiesValue)
-			proptools.ZeroProperties(newValue.Elem())
+			newValue := proptools.CloneEmptyProperties(propertiesValue)
 			v.Set(newValue)
 		})