Reported at https://wimlib.net/forums/viewtopic.php?f=1&t=562.
m4_esyscmd() needs to be m4_esyscmd_s(), so that the version string
doesn't get a trailing newline. It works for me either way, but that's
probably because in autoconf 2.70, AC_INIT started trimming extra
whitespace from its arguments (as per the release notes at
https://lists.gnu.org/archive/html/autotools-announce/2020-12/msg00001.html).
So presumably this fix is needed for older versions of autoconf.
git://wimlib.net / wimlib / commit