gta4xl: Add updatable_apex.mk

The product abstracts configs that need to be set to support updating of APEXes.

Change-Id: Id5aa944ceba6a6846308f1c18a08af8b3bb38589
diff --git a/lineage_gta4xl.mk b/lineage_gta4xl.mk
index 3b18507..690bfd5 100644
--- a/lineage_gta4xl.mk
+++ b/lineage_gta4xl.mk
@@ -17,6 +17,9 @@
 ### LINEAGE
 $(call inherit-product, vendor/lineage/config/common_full_phone.mk)
 
+# Enable updating of APEXes
+$(call inherit-product, $(SRC_TARGET_DIR)/product/updatable_apex.mk)
+
 ## Device identifier. This must come after all inclusions
 PRODUCT_NAME := lineage_gta4xl
 PRODUCT_DEVICE := gta4xl