Fix Makefile typo: trailing spaces are significant

At least, they are significant when followed by a comment?
Switch to running Nuitka from source

Running Nuitka directly from source, with /usr/bin/python2.7 and not
from inside of a virtual directory, turns out to be crucial for
"--standalone" because the custom site.py of a virtualenv will confuse
Nuitka.  See: http://bugs.nuitka.net/issue126