Move apache-xml to external. (project 3 of 4)

Change-Id: Ib65348e4203e6ac653e9fe81369b21dad06b5b58
http://b/3351604
diff --git a/core/dex_preopt.mk b/core/dex_preopt.mk
index 6e0b093..87bf2d3 100644
--- a/core/dex_preopt.mk
+++ b/core/dex_preopt.mk
@@ -4,7 +4,7 @@
 ####################################
 
 # TODO: replace it with device's BOOTCLASSPATH
-DEXPREOPT_BOOT_JARS := core:bouncycastle:ext:framework:android.policy:services:core-junit
+DEXPREOPT_BOOT_JARS := core:apache-xml:bouncycastle:ext:framework:android.policy:services:core-junit
 DEXPREOPT_BOOT_JARS_MODULES := $(subst :, ,$(DEXPREOPT_BOOT_JARS))
 
 DEXPREOPT_BUILD_DIR := $(OUT_DIR)