bah!
I have been working in the oscogvm/unixbuild directory and only now noticed the stackbuild/unixbuild tree with its own HowToBuild instructions.
My reasoning now is that Cog is the standard , so "src" and "unixbuild" etc belong to it (as it should) while "special stuff" like StackInterpreter etc are shuffled off to their own little world in stacksrc and stackbuild.
Thanks for your patience.
tty.