Various fixes to scons for linux:
* Better handling of "multiarch" python stuff (libs also need two different paths).
* Fix Opencollada default paths.

Hopefully this won't break anything...

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57127 954f8c5b-7b00-dc11-b283-0030488c597c