Prefer built-in SRFIs over those in packages
Currently when chez-srfi is installed it provides its own versions of e.g.
(srfi :1 lists) which takes precedence over the SRFIs that are provided by e.g. Sagittarius or Larceny. It is probably more reasonable to use the implementation that came with the implementation, especially since chez-srfi currently doesn't have compat libraries for Sagittarius and a some more Schemes.
This can be accomplished by adding to