Suggested `config.nim[s]` switches for debug/release with C or C++ backend

[janAkali]

You can use this syntax, it is used in the default `nim.cfg`:
    
    
    @if release or danger:
      <put flags here>
    @elif debug:
      <put flags here>
    @else:
      <put flags here>
    @end
    
    
    Run