The `staging::exec_path` parameter was supposed to go with 5581d07badbc3867a1509b01fd68cb9599b08180, which doesn't seem to have made it into my PR. I think I mixed up branch names. In any case, it was to support the Solaris 10 platform, which by default includes `wget`, but in a completely arbitrary and not-in-the-path-by-default location.

The intention again is to make staging work out-of-the-box on another platform I use. If that makes sense, the "incorporate it" next step would probably be to cherry-pick 5581d07badbc3867a1509b01fd68cb9599b08180 into this PR. If not, or if in doubt, I think it would be fine to clear it out for now and I'll submit another PR with a clean addition for discussion later.