bug#62723: autogen fails to build on i686-linux

[Andreas Enge <andreas@enge.fr>]

Hello,

autogen fails to build on i686-linux like so, for instance on master commit
c9af27d4ca733b20f09019f1465d3e5fdc1ec724:

libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I../autoopts -DPKGDATADIR=\"/gnu/store/n29inqv3rnwix1jqsxc1gd2yw0q8jkr0-autogen-5.18.16/share/autogen\" -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -Wall -Werror -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings -Wstrict-aliasing=3 -Wextra -Wno-cast-qual -g -O2 -Wno-format-contains-nul -fno-strict-aliasing -c libopts.c  -fPIC -DPIC -o .libs/libopts_la-libopts.o
In file included from libopts.c:48:
usage.c: In function ‘prt_extd_usage.isra’:
usage.c:736:38: error: ‘s ’ directive output may be truncated writing 2 bytes into a region of size between 0 and 9 [-Werror=format-truncation=]
  736 |         snprintf(vfmt, sizeof(vfmt), vfmtfmt, (unsigned int)nmlen + 4);
      |                                      ^~~~~~~
usage.c:736:9: note: ‘snprintf’ output between 9 and 18 bytes into a destination of size 12
  736 |         snprintf(vfmt, sizeof(vfmt), vfmtfmt, (unsigned int)nmlen + 4);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

The version we package from
   https://ftp.gnu.org/pub/gnu/autogen/
dates from 2018. The website
   https://www.gnu.org/software/autogen/
has apparently not been updated since 2015.

I wonder if we had not better drop this apparently unmaintained software,
but it has quite a lot of dependents:
Building the following 1275 packages would ensure 2489 dependent packages are rebuilt

Andreas