Fix incremental builds

To cut build times in half if INCREMENTAL_BUILDS=true is enabled.

Bug: 27711635
Change-Id: I45a918b3bbb6c9e60f6ff93c7f00915f0e0d865f
diff --git a/packages/SystemUI/Android.mk b/packages/SystemUI/Android.mk
index 258c82e..8c1ce24 100644
--- a/packages/SystemUI/Android.mk
+++ b/packages/SystemUI/Android.mk
@@ -43,9 +43,11 @@
 
 LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
-ifneq ($(SYSTEM_UI_INCREMENTAL_BUILDS),)
+ifneq ($(INCREMENTAL_BUILDS),)
     LOCAL_PROGUARD_ENABLED := disabled
     LOCAL_JACK_ENABLED := incremental
+    LOCAL_DX_FLAGS := --multi-dex
+    LOCAL_JACK_FLAGS := --multi-dex native
 endif
 
 include frameworks/base/packages/SettingsLib/common.mk