Disallow accessing Treble _OVERRIDE reqs.

If something needs to distinguish between _OVERRIDE and non-_OVERRIDE,
it is a hack (these should be the same property).

Bug: 114488870
Test: m nothing (exercises this)
Test: searching all of these reqs in the code.
Change-Id: Idc22150a3179d025d7d95beafad39e8b07946ef8
diff --git a/core/config.mk b/core/config.mk
index b114462..676f325 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -819,12 +819,16 @@
 PRODUCT_FULL_TREBLE_OVERRIDE ?=
 $(foreach req,$(requirements),$(eval $(req)_OVERRIDE ?=))
 
+# TODO(b/114488870): disallow PRODUCT_FULL_TREBLE_OVERRIDE from being used.
 .KATI_READONLY := \
     PRODUCT_FULL_TREBLE_OVERRIDE \
     $(foreach req,$(requirements),$(req)_OVERRIDE) \
     $(requirements) \
     PRODUCT_FULL_TREBLE \
 
+$(KATI_obsolete_var $(foreach req,$(requirements),$(req)_OVERRIDE) \
+    ,This should be referenced without the _OVERRIDE suffix.)
+
 requirements :=
 
 # BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED can be true only if early-mount of