This is similar to the problem mentioned in Automake not generating Makefile.in in subdirs. However, it is subtly different.
I have a simple project with a Makefile in . and one in ./tests/.
In ./Makefile.am I have:
SUBDIRS = tests
In ./configure.ac I have:
AC_CONFIG_FILES([Makefile tests/Makefile ])
AC_CONFIG_HEADER([config.h])
When I run on MacOS or on Ubuntu 20.04 (locally in a VM), both ./Makefile.in and ./tests/Makefile.in are created.
But when I run on GitHub Actions, tests/Makefile.in is not created.
All systems have similar versions of autoconf, aclocal, libtool, and automake.
So what could be different?
