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.

	* gnulib/argp-ba.c: New file.
	* gnulib/argp-eexst.c: Likewise.
	* gnulib/argp-fmtstream.c: Likewise.
	* gnulib/argp-fmtstream.h: Likewise.
	* gnulib/argp-fs-xinl.c: Likewise.
	* gnulib/argp-help.c: Likewise.
	* gnulib/argp-namefrob.h: Likewise.
	* gnulib/argp-parse.c: Likewise.
	* gnulib/argp-pin.c: Likewise.
	* gnulib/argp-pv.c: Likewise.
	* gnulib/argp-pvh.c: Likewise.
	* gnulib/argp-version-etc.c: Likewise.
	* gnulib/argp-version-etc.h: Likewise.
	* gnulib/argp-xinl.c: Likewise.
	* gnulib/argp.h: Likewise.