[lmm]

> Unconditionally autoreconfing things would be better, but risk breakage because the backwards compatibility story in Autotools has historically not been good, because they’re not supposed to be used that way.

Yes and no. "make -f Makefile.cvs" has been a supported workflow for decades. It's not what the "build from source" instructions will tell you to do, but those instructions are aimed primarily at end users building from source who may not have M4 etc. installed; developers are expected to use the Makefile.cvs workflow and I don't think it would be too unreasonable to expect dedicated distro packagers/build systems (as distinct from individual end users building for their own systems) to do the same.