[bug#32933] [PATCH] guix: add license prefix hackage imports

[Joe Hillenbrand <joehillen@gmail.com>]

Sorry, I meant to add justification in the commit message, but apparently I
forgot.

The motivation was to be consistent with the `gnu/packages/haskell.scm` which
uses the `license:` prefix. I noticed this when I imported a bunch of packages
and all of them were missing the prefix, which then had to be manually added.

On Fri, Oct 12, 2018 at 6:17 AM Ludovic Courtès <ludo@gnu.org> wrote:
>
> No strong opinion, but apparently none of the importers currently adds
> the ‘license:’ prefix and I’d rather keep that consistent, one way or
> another.

That's not entirely true. crate calls `spdx-string->license` which adds the
prefix, but it doesn't appear to actually work because it looks for the license
in the wrong part of the json output from crates.io.

I'd be happy to add it to the other importers as it looks like almost all of
`gnu/packages/*.scm` has the `license:` prefix. If so, should I do them all
in a new patch?

Thanks,
Joe