Get rid of obsolete Make variable TARGET_CORE_JARS.

Test: aosp_walleye-userdebug boots.

Bug: 147579140

Change-Id: Ibed8c8479b9c1f3ac333c66aeddea4f5f06c9aad
Merged-In: Ibed8c8479b9c1f3ac333c66aeddea4f5f06c9aad
(cherry picked from commit c46e0673d0568861a634456f72bac2de9805b990)
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 77a5d53..5ff92ac 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -312,8 +312,8 @@
     tz_version_host \
     tz_version_host_tzdata_apex \
 
-ifeq ($(TARGET_CORE_JARS),)
-$(error TARGET_CORE_JARS is empty; cannot initialize PRODUCT_BOOT_JARS variable)
+ifeq ($(ART_APEX_JARS),)
+$(error ART_APEX_JARS is empty; cannot initialize PRODUCT_BOOT_JARS variable)
 endif
 
 # The order matters for runtime class lookup performance.