Revert "Remove support of disabling Jack."

This reverts commit ba068f48727dee2223b3be3b0359accb949e363d.

Test: builds
Change-Id: I2c4d64e26c2e4ceb710a39de2ee9749160d33a72
diff --git a/Android.mk b/Android.mk
index a798a31..bf3d226 100644
--- a/Android.mk
+++ b/Android.mk
@@ -513,6 +513,7 @@
 
 LOCAL_MODULE := framework
 
+LOCAL_DX_FLAGS := --core-library --multi-dex
 LOCAL_JACK_FLAGS := --multi-dex native
 
 LOCAL_RMTYPEDEFS := true
@@ -1348,6 +1349,8 @@
 LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE := ext
 
+LOCAL_DX_FLAGS := --core-library
+
 ifneq ($(INCREMENTAL_BUILDS),)
     LOCAL_PROGUARD_ENABLED := disabled
     LOCAL_JACK_ENABLED := incremental