title: Any way in CMake to require GCC version 4+?
body: <p>I am using some features that are provided in GCC v4+ and would like CMake to find GCC v4 compiler and if it does not find it, return an error stating GCC v4 is required.</p>
  
  <p>Anyone have any modules / ideas on how to do something like this?</p>
  
  <p>Thanks.</p>