How to Enable NEON in OpenCV by using ndk-build on Android Platform?

I am new to Android platform. I have already included openCV library in my c++ code and successfully built an .so file by using ndk-build command. The app has already successfully run on my android phone. My question is how to enable NEON for a better performance? I have already included “LOCAL_ARM_NEON := true” in my .mk file but it did not seem to work. I will really appreciate your help!

undeclared crosspost: