Add flag-guarding also to compat modules

Bug: 353121021
Test: m selinux_policy
Change-Id: I88db84063966fd4fe3d4d11b0be5ea1822d57a0d
diff --git a/flagging/Android.bp b/flagging/Android.bp
index 26e8989..cf6ded1 100644
--- a/flagging/Android.bp
+++ b/flagging/Android.bp
@@ -43,7 +43,7 @@
     name: "se_policy_conf_public_flags_defaults",
     srcs: [":sepolicy_flagging_macros"],
     build_flags: ["all_selinux_flags"],
-    board_api_level_guard: true,
+    board_api_level: "vendor",
 }
 
 contexts_defaults {