Sorry, please disregard the last patch, it was a non-working version.  I
tested this one with Grub and the boot-parameters test (for the label
modification).

I leave the open points for reference.

Miguel Ángel Arruga Vivas <rosen644835@gmail.com> writes:
> (...)
> It brings the whole glibc-locales to the grub and extlinux configuration
> builders, and changes again boot-parameters.  It would be optimal to
> create a minimal locale with the desired locale, as glibc-utf8-locales
> doesn't work with my to-go test target (es_ES.utf8) because setlocale
> raises an exception.
>
> I have in my TODO list to extract translate-label somewhere else, even
> though I'm not sure where could it fit, and to sanitize some inputs to
> ensure the correct generation.  The latter should be ready this week,
> the first depends on finding (or creating) the right place.

Happy hacking!
Miguel