Quoting the commit message
Autoconf 2.71 on Fedora 36 and Ubuntu 22.04 LTS has started reporting
a number of warnings about configure.ac containing obsolete macros. One
of them is this:
$ ./autogen.sh
...
Processing ./configure.ac
configure.ac:17: warning: The macro `AC_PROG_LIBTOOL' is obsolete.
configure.ac:17: You should run autoupdate.
m4/libtool.m4:99: AC_PROG_LIBTOOL is expanded from...
configure.ac:17: the top level
...