common: Make it compile

* Provide our own hal_attribute macro but without neverallows
* Workaround silly issue when compiling system_ext public sepolicy
  without any rules

Change-Id: Id7eb04bd049b13380e69a0367fb588f226a93980
diff --git a/sepolicy/public/attributes b/sepolicy/public/attributes
index 3c736eb..8add675 100644
--- a/sepolicy/public/attributes
+++ b/sepolicy/public/attributes
@@ -1 +1,2 @@
-hal_attribute(omni_fod)
+# HALs
+hal_attribute_omni(omni_fod)