system_server: allow appending to `debuggerd -j` pipe.

Test: debuggerd -j `pidof system_server`
Change-Id: I6cca98b20ab5a135305b91cbb7c0fe7b57872bd3

private/system_server.te

@@ -375,6 +375,10 @@ unix_socket_connect(system_server, tombstoned_java_trace, tombstoned)
 allow system_server tombstoned:fd use;
 allow system_server dumpstate:fifo_file append;
 allow system_server incidentd:fifo_file append;
+# Write to a pipe created from `adb shell` (for debuggerd -j `pidof system_server`)
+userdebug_or_eng(`
+  allow system_server su:fifo_file append;
+')
 
 # Read /data/misc/incidents - only read. The fd will be sent over binder,
 # with no DAC access to it, for dropbox to read.