Looks like libgcrypt.m4 was modified in gnulib a couple days ago (from AC_HELP_STRING to AS_HELP_STRING), but in theory it's supposed to be synced with the libgcrypt repository. Help?
--- libgcrypt/src/libgcrypt.m4 2020-03-31 09:57:48.000000000 -0700 +++ gnulib/m4/libgcrypt.m4 2020-09-28 00:24:10.741933569 -0700 @@ -1,3 +1,3 @@ # libgcrypt.m4 - Autoconf macros to detect libgcrypt -# Copyright (C) 2002, 2003, 2004, 2011, 2014, 2018 g10 Code GmbH +# Copyright (C) 2002, 2003, 2004, 2011, 2014, 2018, 2020 g10 Code GmbH # @@ -11,3 +11,3 @@ # -# Last-changed: 2018-11-13 +# Last-changed: 2020-09-27 @@ -32,3 +32,3 @@ AC_ARG_WITH(libgcrypt-prefix, - AC_HELP_STRING([--with-libgcrypt-prefix=PFX], + AS_HELP_STRING([--with-libgcrypt-prefix=PFX], [prefix where LIBGCRYPT is installed (optional)]),