Untie MultinetworkApiTest from platform libc++.so

Bug: http://b/26512135
Change-Id: Ia01fd851fd7d2e50708620adf11d904e42de0b3b
diff --git a/tests/cts/net/Android.mk b/tests/cts/net/Android.mk
index 6524871..56729b6 100644
--- a/tests/cts/net/Android.mk
+++ b/tests/cts/net/Android.mk
@@ -27,7 +27,7 @@
 LOCAL_JAVA_LIBRARIES := voip-common conscrypt org.apache.http.legacy
 
 LOCAL_JNI_SHARED_LIBRARIES := libcts_jni libnativedns_jni \
-                              libnativemultinetwork_jni
+                              libnativemultinetwork_jni libnativehelper_compat_libc++
 
 # include CtsTestServer as a temporary hack to free net.cts from cts.stub.
 LOCAL_SRC_FILES := $(call all-java-files-under, src)