bug#45180: Building automake 1.16.3 with autoconf 2.70 fails

[FX]

On macOS (all supported versions from 10.14 to 11.0), building automake 1.16.3 
with the newly released autoconf 2.70 fails. The error is the following:

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.


See the full build output at https://savannah.gnu.org/support/index.php?110397 
I do not know whether this is a autoconf or automake issue, but the two tools 
should work together, shouldn’t they?

FX