unconfined_additional: add policy module

unconfined_additional.te

@@ -0,0 +1,9 @@
+policy_module(unconfined_additional, 0.0.1)
+
+require {
+  type unconfined_t;
+  type portage_sandbox_t;
+}
+
+allow unconfined_t portage_sandbox_t:process transition;
+allow unconfined_t self:process execmem;