Default NDK modules to libc++_shared.

Test: make native
Bug: None
Change-Id: I9ca2313c2082e9841a20e240ffca84219a419d49
diff --git a/core/binary.mk b/core/binary.mk
index 2f306b2..c468079 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -187,7 +187,7 @@
   endif
   LOCAL_NDK_STL_VARIANT := $(strip $(LOCAL_NDK_STL_VARIANT))
   ifeq (,$(LOCAL_NDK_STL_VARIANT))
-    LOCAL_NDK_STL_VARIANT := system
+    LOCAL_NDK_STL_VARIANT := c++_shared
   endif
   ifneq (1,$(words $(filter none system stlport_static stlport_shared c++_static c++_shared gnustl_static, $(LOCAL_NDK_STL_VARIANT))))
     $(error $(LOCAL_PATH): Unknown LOCAL_NDK_STL_VARIANT $(LOCAL_NDK_STL_VARIANT))