Use two-column format for PRODUCT_BOOT_JARS components.

The first component is the apex name, or a special name "platform"
if the boot jar is a platform jar rather than a part of some apex.
This is a prerequisite change for moving core-icu4j to a separate
com.android.i18n apex.

Old one-column format is still supported, but all unqualified
components of PRODUCT_BOOT_JARS get "platform:" prepended to them
after reading the product makefiles.

Test: aosp_walleye-userdebug boots
Bug: 138994281
Change-Id: I0f79c7d10477880ca65354251a5d1ca0b7ce79ab
diff --git a/core/envsetup.mk b/core/envsetup.mk
index 6e75a18..7dd19cf 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -258,7 +258,13 @@
 # java code with dalvikvm/art.
 # Jars present in the ART apex. These should match exactly the list of
 # Java libraries in the ART apex build rule.
-ART_APEX_JARS := core-oj core-libart core-icu4j okhttp bouncycastle apache-xml
+ART_APEX_JARS := \
+    com.android.art:core-oj \
+    com.android.art:core-libart \
+    com.android.art:core-icu4j \
+    com.android.art:okhttp \
+    com.android.art:bouncycastle \
+    com.android.art:apache-xml
 #################################################################
 
 # Read the product specs so we can get TARGET_DEVICE and other