argp_help attempts to translate empty string, which results in printing
meta information about translation, like in
bor@opensuse:~/build/grub> grub2-mknetdir --help
Использование: grub2-mknetdir [ПАРАМЕТР…]
Project-Id-Version: grub 2.02-pre2
Report-Msgid-Bugs-To: bug-grub@gnu.org
...
Update gnulib/argp-help.c to the current version which fixes this
(commit b9bfe78424b871f5b92e5ee9e7d21ef951a6801d).
New function.
(add_length): Likewise.
(__argp_fmtstream_update): Handle strings with non-ASCII chars.
* grub-core/gnulib/argp-fmtstream.h (__argp_get_display_len): New
proto.
* grub-core/gnulib/argp-help.c (argp_args_usage): Use
__argp_get_display_len.
