[pypy-dev] Advice on code location

Hi I'm trying to use Python to build PyPy. One problem I noticed is the search paths for modules is not the same For PyPy and Python. I want to add code to the build process that will check if PyPy or Python is running. If Python is running, add paths to sys.path that would enable Python to find needed modules. Which file would be a good place to add such code? Thank you.