title: Detect underlying platform/flavour in Cmake
body: <p>Does anybody know any cmake variable or hook or something which can give me underlying platform name/flavour name on which it is getting executed ?
  e.g. Linux-CentOs
  Linux-Ubuntu
  Linux-SLES</p>
  
  <p>I know cmake has "CMAKE_SYSTEM" variable but that doesn't help differentiating flavours of linux for e.g. Any help is appreciated.</p>
  
  <p>edit :
  I just read that it can be done using lsb_release command ?</p>