(main.o):(.text.startup+0xa0): undefined reference to `WinMain@16'

Question

I have the following folder structure:

Basically, I tried the following commands to compile my C++ code:

mkdir build
cd ./build
cmake-G "MinGW Makefiles"
make 

When I compile the C++ library code for my model, I get this error.

Please help me figure out what I am doing wrong.