goto-instrument's options require two file arguments and when not supplied, fails with a non-obvious help message

[NlightNFotis]

goto-instrument, as mentioned in #2793, needs two file arguments passed for most of the command line arguments it supports (given it's just transformations that are read from one goto-binary, applied, and then written to another goto-binary). When it's not given two file arguments for these options, it fails with its generic --help message, failing to make obvious what has gone wrong.