Your render loop is executed no matter what mimimization state of your window is.
If you want to stop rendering, you have to enhace the application logic a bit to track the state your window is in. GLFW supports user-defined a callback for such things with glfwSetWindowIconifyCallback()
so your application can get noticed when the window is minimized or restored. You can the decide to stop the render loop, and can use glfwWaitEvents()
to wait for something to happen (like the window being restored) without using all available CPU time.