Busted tests fail if lua interpreter specified

[alerque]

Noted while packaging for Arch Linux (which has packages for 4 Lua versions):

# works
$ busted

# fails
$ busted --lua lua

Specifying any Lua interpreter (even if it happens to be the default) causes one failure:

[  FAILED  ] spec/app_spec.lua @ 7: pl.app.lua should pick up the arguments used to run this test

[Tieske]

I guess that's because both Busted and Penlight try and fiddle with the global args