title: Correct way to use third-party libraries in cmake project
body: <p>I'm working on project that use some third-party libraries. I can clone and put them into my project as a <code>git submodule</code> and use <code>add_subdirectory</code> to use them in my project. But it take much time to compile these libs, and I can not manage <code>cmake</code> variables in my projects, and <code>install()</code> command make my package contains many things that I don't need.</p>
  
  <p>So what is correct way to use third-party libraries in my project. I can not tell the client to install these libraries as dependencies of my project.</p>