Use two-column format for ART_APEX_JARS components.

This is to unify ART_APEX_JARS format with the new 2-column
PRODUCT_BOOT_JARS format. The first component is the ART apex name.
This is a prerequisite change for moving core-icu4j to a separate
com.android.i18n apex.

Test: aosp_walleye-userdebug boots
Bug: 138994281
Change-Id: I7159260d1f46094857de52b21335defd352ca9b7
diff --git a/Android.mk b/Android.mk
index 37e4a34..5ae5881 100644
--- a/Android.mk
+++ b/Android.mk
@@ -733,7 +733,8 @@
 ########################################################################
 # Phony target for building what go/lem requires for syncing /system to target.
 .PHONY: build-art-unbundled-golem
-build-art-unbundled-golem: art-runtime linker oatdump $(ART_APEX_JARS) conscrypt crash_dump
+art_apex_jars := $(foreach pair,$(ART_APEX_JARS), $(call word-colon,2,$(pair)))
+build-art-unbundled-golem: art-runtime linker oatdump $(art_apex_jars) conscrypt crash_dump
 
 ########################################################################
 # Rules for building all dependencies for tests.