This was originally used because we needed a lua interpreter to run the
standalone _busted_ lua application (except we used fuckery behind the
scenes to fake its binary dependencies with our own binary
dependencies). Now we longer do that, we instead run `test.harness` as a
standard nvim -l script. as this mode is no longer used in tests it
risks going to bitrot anyway.
NB: -ll mode still had some theoretical benefits like quicker
initialization and more "native" printing behavior, etc.
But we can incrementally work on "nvim -l" mode instead
of maintaining a separate special thing.
03aff28b73
