[libclc] r200413 - Enforce python2 for systems that use python3 as their default.

[Daniel Liew]

> Was the original purpose of this patch to fix the build with python3?
> If yes, is there some other solution?

Yes python3 (configure.py doesn't work with this) is my default but I
have python2 installed too (which configure.py does work with).

A solution would be to clean up the python script to work correctly
with Python 3.x and 2.7.x but I was feeling lazy so I just changed the
shebang to use /usr/bin/python2 . I'm not sure if it's possible to
support 2.4 (eurgh... that's almost 10 years old) all the way to 3.3.

I and other in my situation quite easily just do

$ python2 ./configure.py

instead with the old shebang in configure.py and things work fine.
It's more just a convenient to not have to write ``python2``. If it is
causing too many issues you can simply revert r200413.

Thanks,
Dan.