Generates SDK stubs of android-support-multidex

(cherry picked from commit c4441b8c3701147365213a1f789626a8d442db6e)

Conflicts:
        core/pathmap.mk

Change-Id: I9283e793d8cdbd4003b86fd33ff62dd35c663f1f
diff --git a/core/pathmap.mk b/core/pathmap.mk
index 28661c2..2b97dbf 100644
--- a/core/pathmap.mk
+++ b/core/pathmap.mk
@@ -110,7 +110,8 @@
         v7/appcompat \
         v7/mediarouter \
         v8/renderscript \
-        v13
+        v13 \
+        multidex
 
 #
 # A version of FRAMEWORKS_SUPPORT_SUBDIRS that is expanded to full paths from