message: Make Python version setting actually effective
  This needs to be outside the if to actually work. Also, this adjusts the
  list of versions to match LLVM.
  Patch by: Christian Biesinger
diff: @@ -87,8 +87,8 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
  include(CheckAtomic)
  include(LLVMDistributionSupport)
  + set(Python_ADDITIONAL_VERSIONS 3.7 3.6 3.5 2.7)
  if (PYTHON_EXECUTABLE STREQUAL "")
  - set(Python_ADDITIONAL_VERSIONS 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0 2.7 2.6 2.5)
  include(FindPythonInterp)
  if( NOT PYTHONINTERP_FOUND )
  message(FATAL_ERROR
  