package store directory in custom location

[Andy Tai]

Hi, is it possible to have  a /gnu/store/ directory for a package in a
custom path?  A usage scenario is, say, to have a python interpreter,
with its package directory that normally exists as
/gnu/store/<something>, to be somewhere I specified, so it would be
possible to use that python with python's package manager to install
python modules as site packages specific to this python (as it is not
easy to have all python modules available as packages in Guix)

If this python can only run from the /gnu/store/... directory, trying
to install site packages would normally fail (as /gnu/store/... is
read only to non root user) and not good practice anyway (as
/gnu/store/... is not meant to be user touched but only managed by
Guix)