Build libnativemultinetwork_jni with C++

Test: atest MultinetworkApiTest
Change-Id: If34a89cf00aa06590d947696fc647fc26aa019e8
diff --git a/tests/cts/net/jni/Android.mk b/tests/cts/net/jni/Android.mk
index 727a44d..ccb1278 100644
--- a/tests/cts/net/jni/Android.mk
+++ b/tests/cts/net/jni/Android.mk
@@ -36,7 +36,7 @@
 LOCAL_MODULE := libnativemultinetwork_jni
 # Don't include this package in any configuration by default.
 LOCAL_MODULE_TAGS := optional
-LOCAL_SRC_FILES := NativeMultinetworkJni.c
+LOCAL_SRC_FILES := NativeMultinetworkJni.cpp
 LOCAL_CFLAGS := -Wall -Werror -Wno-format
 LOCAL_C_INCLUDES := $(JNI_H_INCLUDE)
 LOCAL_SHARED_LIBRARIES := libandroid libnativehelper_compat_libc++ liblog