Include android-support-multidex in SDK libs.

(cherry picked from commit 9e27887b60e2e3ae1ea94a8c093e6e493f72c8e4)

Change-Id: Ieb2901a633a687927a0c5a5db6d17896c3b86449
diff --git a/build/Android.mk b/build/Android.mk
index f8578d2..89bee2b 100644
--- a/build/Android.mk
+++ b/build/Android.mk
@@ -143,7 +143,8 @@
     android-support-v7-gridlayout \
     android-support-v7-appcompat \
     android-support-v7-mediarouter \
-    android-support-v13
+    android-support-v13 \
+    android-support-multidex
 
 $(foreach lib, $(ANDROID_SUPPORT_LIBRARIES), $(eval $(call _package_sdk_library,$(lib))))