Link error while trying to use glLoadGen

While reading the OpenGL 4 Shading Language Cookbook, I encountered the OpenGL Loader Gen library and immediately wanted to try it out. I started creating a small example program that you can see underneath.

#include "GLFW/glfw3.h"
#include "GL/gl_core_4_1.hpp"

namespace engine
{
    class Window
    {
    private:
        const unsigned int width;

        const unsigned int height;

        const char *title;

        const void refresh()
        {
            glfwSwapBuffers(this -> glfwWindow);
            glfwPollEvents();
        }
    protected:
        GLFWwindow *glfwWindow;
    public:
        Window(const unsigned int width, const unsigned int height, const char title[]): width(width), height(height), title(title)
        {
            if (glfwInit() != GLFW_TRUE)
            {
                throw "Couldn't initialise the required GLFW library.";
            }
            glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
            glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
            glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
            glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
            if (this -> glfwWindow)
            {
                throw "Cannot create a secondary window.";
            }
            this -> glfwWindow = glfwCreateWindow(this -> width, this -> height, this -> title, NULL, NULL);
            // This is the crucial line that will stop the program from compiling.
            gl::exts::LoadTest context = gl::sys::LoadFunctions();
            if (!context)
            {
                throw "Couldn't initialse the required GL library.";
            }
            glfwMakeContextCurrent(this -> glfwWindow);
            glfwSwapInterval(GLFW_TRUE);
            if (!glfwWindow)
            {
                glfwTerminate();
                throw "Couldn't create a new initially empty window.";
            }
        }

        const bool await()
        {
            this -> refresh();
            if (glfwWindowShouldClose(this -> glfwWindow))
            {
                glfwDestroyWindow(this -> glfwWindow);
                glfwTerminate();
                return false;
            }
            return true;
        }
    };
}

int main(const int argc, const char *argv[])
{
    engine::Window window(1280, 720, "Foundation");
    while (window.await())
    {
    }
    return 0x00000000;
}

My next step was to try compiling the program with the LLVM compiler on computer running on the macOS High Sierra operating system.

clang++ -o Application.exec Subdirectory/*.cpp -lglfw -framework Cocoa -framework OpenGL -framework IOKit -framework CoreVideo

However, during compilation I receive the following unexpected linker error:

Undefined symbols for architecture x86_64:
  "gl::sys::LoadFunctions()", referenced from:
      engine::Window::Window(unsigned int, unsigned int, char const*) in Application-58a670.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Here is my actual question: how do I let the program shown above compile using the previously mentioned OpenGL Loader Gen library?

from the docs

The above command line will generate gl_core_3_3.h and gl_core_3_3.c files. Simply include them in your project; there is no library to build, no unresolved externals to filter through.

You need to run their generator to produce those source files.