title: How to build several configurations at once with CMake?
body: <p>E.g. how should I build release and debug version at the same time? I guess the answer make use of cache variables and some kind of "collection" of them. 
  Is it common way to get configuration params from cache params, isn'it ? If the answer is yes, how should I use several "collections" of them in a best way ?
  Thanks a lot!</p>