[bug#55606] [PATCH 2/2] gnu: Add hare.

[(]

Some notes:

+ `hare` is not a compiler for Hare, it's a build tool. (It's going to
  include a self-hosted compiler eventually though :))
+ I think the way this patch handles config.mk from `hare` is better.
+ The Guix 'R Us version works with cross-compilation; I don't think this
  one does?
+ harec and qbe probably shouldn't be propagated; their paths should be
  patched into the source code.

    -- (