Add comments on compat files

To prevent further confusion.

Bug: 258029505
Test: manual
Change-Id: Iaa145e4480833a224b1a07fc68adb7d3e8a36e4b
diff --git a/private/compat/29.0/29.0.compat.cil b/private/compat/29.0/29.0.compat.cil
index ccd9d1a..0bb2ae8 100644
--- a/private/compat/29.0/29.0.compat.cil
+++ b/private/compat/29.0/29.0.compat.cil
@@ -1,3 +1,7 @@
+;; complement CIL file for compatibility between ToT policy and 29.0 vendors.
+;; will be compiled along with other normal policy files, on 29.0 vendors.
+;;
+
 (typeattribute vendordomain)
 (typeattributeset vendordomain ((and (domain) ((not (coredomain))))))
 (allow vendordomain self (netlink_route_socket (nlmsg_readpriv)))