message: version check improvement
  Stop cmake processing if version is not detect correctly, there is no need to continue any more because it will already fail when trying build bsoncxx and will show more unnecessary error to the screen.
diff: @@ -157,10 +157,7 @@ if(BUILD_VERSION STREQUAL "0.0.0")
  )
  if(NOT CALC_RELEASE_VERSION_RESULT STREQUAL 0)
  # If python failed above, stderr would tell the user about it
  - message(WARNING
  - "BUILD_VERSION not specified and could not be calculated\
  - (script invocation failed); setting library version to 0.0.0"
  - )
  + message(FATAL_ERROR "BUILD_VERSION not specified and could not be calculated")
  else()
  set(BUILD_VERSION ${CALC_RELEASE_VERSION})
  file(WRITE ${CMAKE_BINARY_DIR}/VERSION_CURRENT ${CALC_RELEASE_VERSION})
  