-get-gcp-jwt: clean up references, use +ot
-get-gcp-jwt: clean up references, use +ot

Moves =, closer to call sites so it's clearer what's coming from where.
Also uses +ot, allowing a less horrifying +sign-jwt. This also seems to
not jump back and forth between tapes and cords as much, for what that's
worth.

urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit