Add persist.sysui.notification.builder_extras_ovrd

Adds persist.sysui.notification.builder_extras_override property
and associated permissions, which will be used to flag guard
a change in core/...Notification.java.

Permissions are limited in scope to avoid unnecessary access.
Apps may need to read the flag (because Notification.java
is a core library), but setting should only be possible
internally (and via debug shell).

Test: manual flash+adb setprop/getprop
Bug: 169435530
Change-Id: I3f7e2220798d22c90f4326570732a52b0deeb54d
diff --git a/private/system_server.te b/private/system_server.te
index 27e5594..515dd13 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -836,6 +836,9 @@
 # Read persist.wm.debug. properties
 get_prop(system_server, persist_wm_debug_prop)
 
+# Read persist.sysui.notification.builder_extras_override property
+get_prop(system_server, persist_sysui_builder_extras_prop)
+
 # Read ro.tuner.lazyhal
 get_prop(system_server, tuner_config_prop)
 # Write tuner.server.enable