libtool 2.2.6a unnecessary AC_CONFIG_M4_DIR warning?

[Simon Josefsson]

I'm trying to move from libtool 1.5 to libtool 2.2 again (last time
mingw+wine builds didn't work, but this seems to work now, thanks!) and
noticed I get a new warning message:

libtoolize: Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
libtoolize: rerunning libtoolize, to keep the correct libtool macros in-tree.

I can't seem to find any difference between using that in configure.ac
or not, all the same *.m4 files are distributed in m4/.

Note that I have in Makefile.am:

ACLOCAL_AMFLAGS = -I m4 -I gl/m4 -I lib/gl/m4

I recall that some tools already assume the first -I<dir> in
ACLOCAL_AMFLAGS is the place to put more *.m4 files, so can't libtool
make this assumption too?

I'm trying to avoid having to maintain redundant configuration
statements in my packages, so fixing this would help with that.

Thanks,
/Simon