Add rules to cover memfd's for testing.

Bug: 193885716
Test: Presubmit passes for CL:1770125
Change-Id: I3a5c6be5e59169df4c5c513626106fb6f350a118
diff --git a/private/shell.te b/private/shell.te
index 2f983f2..e8d0b2b 100644
--- a/private/shell.te
+++ b/private/shell.te
@@ -184,6 +184,11 @@
 # Allow shell to access the keystore2_key namespace shell_key. Mainly used for native tests.
 allow shell shell_key:keystore2_key { delete rebind use get_info update };
 
+# Allow shell to open and execute memfd files for minijail unit tests.
+userdebug_or_eng(`
+  allow shell appdomain_tmpfs:file { open execute_no_trans };
+')
+
 # Allow shell to write db.log.detailed, db.log.slow_query_threshold*
 set_prop(shell, sqlite_log_prop)