Looks like Tnix has a normal PDP-11 a.out.
dd copied over ran OK and the stock dd.c from the V7 source distribution compiled
and ran.
Discovered more tools that are missing (like nm and strip)
This is interesting because the Tnix cross-development tools I've recovered
(and that others might have on floppy) should be able to be run under SIMH.
So if there are old development project sources floating around, they should
be rebuildable without a 856x