Python PortGroup environment variables

[Sean Farley]

Is there any reason that the configure.env variables are automatically
copied to the build and destroot phases?

I ask because most python packages do not use the traditional
'./configure; make; make install' method and instead set things like the
prefix and whatnot in the build or destroot phase.

Should we just add those variables (CC, CFLAGS, CXX, etc.) to build and
destroot phases?