m4: Update with newer autoconf constructs.
* src/libgcrypt.m4: Replace AC_HELP_STRING to AS_HELP_STRING.
Applied the change in gnulib of commit:
fd082b5cdd9f25000a30ba65e295805b8228df3b
by:
Author: Gavin Smith <gavinsmith0123@gmail.com> Date: Sun Sep 27 21:06:51 2020 +0200
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>