On macOS 15.6.1 (running on 13 inch M3 MacBook Air; Xcode 16.4 installed; apfs as the file system) and with self-compiled versions of GNU m4 1.4.20 and autoconf 2.72 installed, running "make check" for automake 1.18.1 resulted in four unexpected failures.  Three of those appear to be in the t/tap-stderr-prefix tests and the other for t/yacc-bison-skeleton.  A gzipped version of test-suite.log, trimmed to the output for the four unexpected failures, is attached.

automake 1.18.1 had been unpacked in /var/tmp and then configured and built with

env PATH=/Users/eric/Documents/extern/autoconf-2.72/bin:"$PATH" ./configure \
    --prefix=/Users/eric/Documents/extern/autoconf-2.72
env PATH=/Users/eric/Documents/extern/autoconf-2.72/bin:"$PATH" make
env PATH=/Users/eric/Documents/extern/autoconf-2.72/bin:"$PATH" make check

/Users/eric/Documents/extern/autoconf-2.72 is where m4 1.4.20 and autoconf 2.72 had been installed.  "make check" for m4 had reported no unexpected failures.  "make check" for autoconf reported one unexpected failure in "19. tools.at:672: testing autoconf: timestamp changes" which appears to be a known issue with timestamp resolution on macOS.