Build: cpybuilder.py does not use six.py, so remove import

Remove unnecessary import of six.py, so that gcc-python-plugin can be
built (although not tested) without installing six.py.

Author: Kevin Pyle

cpybuilder.py

@@ -17,7 +17,6 @@
 
 from subprocess import Popen, PIPE
 import re
-import six
 
 # For the purpose of the GCC plugin, it's OK to assume that we're compiling
 # with GCC itself, and thus we can use GCC extensions