This recipe will build the "Hello, World" executable from the following source code (hello-world.cpp):

#include <cstdlib>
#include <iostream>
#include <string>

std::string say_hello() { return std::string("Hello, CMake superbuild world!"); }

int main() {
  std::cout << say_hello() << std::endl;
  return EXIT_SUCCESS;
}

The project is structured as follows, with a root CMakeLists.txt, and a src/CMakeLists.txt file:

.
├── CMakeLists.txt
└── src
    ├── CMakeLists.txt
    └── hello-world.cpp