bug#45180: Building automake 1.16.3 with autoconf 2.70 fails

[FX]

> If you have a reproducible recipe starting from the released tarballs,
> let us know.

Sorry if I was unclear. The bug happens with the released tarballs, and it 
entirely reproducible on macOS. We’re reproduced it on different versions of 
the OS, and machines.

While the original poster’s report involved running "autoconf autotest.m4”, the 
same issue happens simply by building automake 1.16.3 with autoconf 2.70 on any 
macOS version.
See my full build output in comment #6 at 
https://savannah.gnu.org/support/index.php?110397#comment6

I was hoping you could give me some directions to debug this problem, I’m 
willing to dig into it but don’t know where to start. For example, the error 
(in config.log) is the following but I don’t know what it means or where it’s 
coming from:


configure:3113: checking whether autoconf works
configure:3121: cd conftest && autoconf -o /dev/null conftest.ac
unknown channel m4trace: -1- _m4_warn(syntax, AC_OUTPUT was never used, )
at /tmp/share/autoconf/Autom4te/Channels.pm line 631.
        Autom4te::Channels::msg("m4trace: -1- _m4_warn(syntax, AC_OUTPUT was 
never used, )\x{a}", undef, undef, "partial", 0) called at /tmp/bin/autom4te 
line 1073
configure:3124: $? = 1
configure:3133: result: no
configure:3136: error: The installed version of autoconf does not work.
    Please check config.log for error messages before this one.


Is AC_OUTPUT required, and if so where should it be included?