Since upgrade to SCons 2.3.0 a small change is needed to ensure 32bit is targeted properly when
building 32bit Blender with 64bit compiler installed as well (MSVC).

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57510 954f8c5b-7b00-dc11-b283-0030488c597c