Add expandattribute to system_and_vendor_property_type

To prevent the attribute from being optimized away.

Test: m selinux_policy
Test: investigate sys/fs/selinux/policy
Change-Id: I5340425f491afdf863d9b670492c0dcb24835932
diff --git a/private/attributes b/private/attributes
index cf1c307..991bac1 100644
--- a/private/attributes
+++ b/private/attributes
@@ -9,3 +9,4 @@
 # and vendor_property_type. Such types are ill-formed because
 # property owner attributes must be exclusive.
 attribute system_and_vendor_property_type;
+expandattribute system_and_vendor_property_type false;