Unset & restoring environment variables functions for eb's

Problem: For bootstrapping gcc CPATH, C_INCLUDE_PATH and LIBRARY_PATH are preferable empty as it can generate nasty build errors when certain libraries are in those paths.

Idea: add some functions that removes a specified env var and restores it after the eb is finished. 

This is not that difficult to do but where is a suitable place? I think tools/environment.py sounds as a logical place. I'm thinking of function:
PrepareEnv( dict env ) with env a dict of all vars that you want set (or unset).
ResetEnv() to undo the changes from PrepareEnv

I also noticed that there are functions to manipulate the environment in tools/utilities.py and tools/filetools.py. Would it make sense to centralized all those functions in tools/environment.py?