scons: compile on systems where python2 and python3 co-exist Compile gem5 on systems where python2 and python3 co-exists without any changes in path. python2-config is chosen over python-config if it exists.
scons: compile on systems where python2 and python3 co-exist
Compile gem5 on systems where python2 and python3 co-exists without any
changes in path. python2-config is chosen over python-config if it exists.

Committed by: Nilay Vaish <nilay@cs.wisc.edu>
(transplanted from 24a198a46ff08475e598d77e2799c71b8588ad2e)

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin