Allow system_server to kill artd and its subprocesses.

This is to make sure that no process is accessing files in chroot when
we teardown chroot.

Bug: 311377497
Test: Set a very short timeout for `ensureNoProcessInDir` and run
  Pre-reboot Dexopt.
Change-Id: I5c60497c73a9d56068e47840ffd4a0f0a550c250
diff --git a/private/system_server.te b/private/system_server.te
index 406c146..e7ae9fc 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -1656,6 +1656,16 @@
 # otapreopt_script is still alive.
 allow system_server postinstall:fifo_file read;
 
+# Allow system_server to kill artd and its subprocesses, to make sure that no process is accessing
+# files in chroot when we teardown chroot.
+allow system_server {
+  artd
+  derive_classpath
+  dex2oat
+  odrefresh
+  profman
+}:process sigkill;
+
 # Do not allow any domain other than init or system server to get or set the property
 neverallow { domain -init -system_server } crashrecovery_prop:property_service set;
 neverallow { domain -init -dumpstate -system_server } crashrecovery_prop:file no_rw_file_perms;