Build the pinned termtris branch (be5b323) with this compiler, assemble
and link it with the TI 1987 GSPA/GSPLNK and RTS.LIB, and run the proven
play_keys board/move/panels/quit paths in MAME with the M4 loader. Add
the contiguous-stack varargs MAME probe and the switch-to-lookup driver
regression check. The termtris build found the i8/i16 argument, i1/
anyext load, nested-data, MULHS and late-GEP gaps fixed in the compiler.