machine-parseable: would one-liner's do? For example:
rts_ways: t, p (use build system codes)
registerised: YES (or 1)
supports_NCG: YES (or 1)
supports_SMP: YES (or 1)
The idea is that all this can go directly from compiler/Makefile into Config.hs into the options. Doesn't need to be after +RTS; might be an argument to ghc --version (no arg means as before; arg with parameter you want returns value like sysctl -n var on Darwin).