how do I build xf86-video-ati

[John Lumby]

I usually build xorg using jhbuild.
The last time I successfully built the xf86-video-ati package was in 2016,
when the cloned build tree contained a complete autoconf setup with an aclocal.m4
and also various other build-related bits and pieces,    and jhbuild ran autogen.sh and ./configure and so on and built it cleanly.

But now there is no aclocal.m4 nor is there an m4 subdirectory, and  autogen.sh fails with
aclocal: error: couldn't open directory 'm4': No such file or directory,  and all my attempts to build it manually,  e.g. pointing the M4PATH at xorg-build/share/aclocal also fail.

Obviously I am missing something or have omitted some step or dependency.   Could someone in the know please point me at the right way to build it.

Thanks     John Lumby