Fix README build instructions
Fix README build instructions

jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit