When we add file in cocos2dx
Include new c++ file in android.mk file.
In this situation use wildcard for do not write one by one.

let's see example,include c++ files in directory name class.
In android.mk file

FILE_LIST := $(wildcard $(LOCAL_PATH)/../../../Classes/*.cpp)

LOCAL_SRC_FILES := hellocpp/main.cpp

LOCAL_SRC_FILES += $(FILE_LIST:$(LOCAL_PATH)/%=%)
	

First only include hellocpp/main.cpp file.
And use wildcard for include all files in Classes

I confirm version 3.16