message: Add CMake option to treat warnings as errors
diff: @@ -156,6 +156,12 @@ else()
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-missing-braces")
  endif()
  + # Enable -Werror if requested
  + if(WARNINGS_AS_ERRORS)
  + set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
  + message(WARNING "Treating all C++ compile warnings as errors!")
  + endif()
  +
  # Issue a warning if AliRoot Core does not have AliEn support (this is wrong in most cases)
  if(NOT AliRoot_HASALIEN)
  message(WARNING "AliRoot Core has been built without with AliEn support: some features might be unavailable!")
  