bug#46191: Add option to make "guix refresh" keep the downloaded files

[Hartmut Goebel]

When running "guix refresh -u some-package" downloads the package to 
update the hash. But the source is not added to the store, Thus when 
running "guix build some-package", the source will be downloaded again.

I'd like to have an option to make "guix refresh" add teh source to the 
store, so it is already available for "guix build".

--
Regards
Hartmut Goebel

| Hartmut Goebel          | h.goebel@crazy-compilers.com               |
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