Add sepolicy prebuilt dirs and variables to config

These are used when we build vendor sepolicy against old plat sepolicy.

Bug: 33691272
Test: build
Change-Id: I847108539b3b9d7d25c0fad9eddc017275a564be
diff --git a/core/config.mk b/core/config.mk
index bfff84e..e146f64 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -840,6 +840,14 @@
 BOARD_SEPOLICY_VERS := $(PLATFORM_SEPOLICY_VERSION)
 endif
 
+ifeq ($(BOARD_SEPOLICY_VERS),$(PLATFORM_SEPOLICY_VERSION))
+IS_TARGET_MIXED_SEPOLICY :=
+else
+IS_TARGET_MIXED_SEPOLICY := true
+endif
+
+.KATI_READONLY := IS_TARGET_MIXED_SEPOLICY
+
 # A list of SEPolicy versions, besides PLATFORM_SEPOLICY_VERSION, that the framework supports.
 PLATFORM_SEPOLICY_COMPAT_VERSIONS := \
     28.0 \