In an effort to shrink and modularize the main scons files, this change pulls the scons and python version checking code out of the main file and into site_init.py which runs before the SConstruct starts. This will be a place to put really generic code which has to do with the very fundemental aspects of getting scons to work. Other checks, like checks for particular tools or particular versions of tools, will happen in other more specialized files. Change-Id: Icd00ecadbe1141aef4dbadcf42d6ddef1f3a701f Reviewed-on: https://gem5-review.googlesource.com/5561 Reviewed-by: Gabe Black <gabeblack@google.com> Maintainer: Gabe Black <gabeblack@google.com>