[Bio-packaging] GEM_PATH

[pjotr.public66 at thebird.nl]

We are using this now:

> GEM_PATH=/home/pjotrp/.guix-profile/lib/ruby/gems/2.2.0/ 

One of the BAD things of Rubygems is that there is no isolation
between ruby versions and their gems. What we are doing here allows
nokogiri to be installed in isolation for 2.1 series and 2.2 series,
but not for minor numbers. I think that is wrong. We should at least
allow for the minor number and patch level.

So

  GEM_PATH=/home/pjotrp/.guix-profile/lib/ruby/gems/2.1.6p34/ 

makes more sense to me. Even better we use the Guix hash. So for
/gnu/store/c13v73jxmj2nir2xjqaz5259zywsa9zi-ruby-2.1.6/bin/ruby it
would become 

  GEM_PATH=/home/pjotrp/.guix-profile/lib/ruby/gems/c13v73jxmj2nir2xjqaz5259zywsa9zi-ruby-2.1.6/

How does that ring to you? Or maybe the shorter form

  GEM_PATH=/home/pjotrp/.guix-profile/lib/ruby/gems/c13v73jxm-ruby-2.1.6/

It would guarantee isolation of gems. No more rvm/rubygem/etc hell.

Pj.