bug#29247: guix complains that Guile-Git is missing

[Marco van Hulten <marco@hulten.org>]

Hello,

I have installed Guile-Git, but guix still complains that it is missing.

```
root@watson ~# guix package -i guile-git                                                                                     
substitute: updating list of substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
...
substitute: updating list of substitutes from 'https://mirror.hydra.gnu.org'... 100.0%                                       
The following package will be installed:                                                                                         guile-git    0.0-4.951a32c   /gnu/store/cjg6sngjq540k38s5l3nfxpydybhpas0-guile-git-0.0-4.951a32c
...
grafting '/gnu/store/2lfalradkpy41cxzk9bk2ssjzklcq8gw-guile-git-0.0-4.951a32c' -> '/gnu/store/cjg6sngjq540k38s5l3nfxpydybhpas0
-guile-git-0.0-4.951a32c'...
Creating manual page database for 3 packages... done in 0.395 s
4 packages in profile
root@watson ~# time guix pull --cores=1
guix pull: error: Guile-Git is missing but it is now required by 'guix pull'.
Install it by running:

  guix package -i guile-git
  export GUILE_LOAD_PATH=$HOME/.guix-profile/share/guile/site/2.2:$GUILE_LOAD_PATH
  export GUILE_LOAD_COMPILED_PATH=$HOME/.guix-profile/lib/guile/2.2/site-ccache:$GUILE_LOAD_COMPILED_PATH


real    0m0.314s
user    0m0.313s
sys     0m0.032s
```

-Marco