Add missing command to the build instructions in the README.
Add missing command to the build instructions in the README.

kaustavha/luvit,boundary/luvit,rjeli/luvit,luvit/luvit,DBarney/luvit,bsn069/luvit,GabrielNicolasAvellaneda/luvit-upstream,boundary/luvit,kaustavha/luvit,GabrielNicolasAvellaneda/luvit-upstream,sousoux/luvit,boundary/luvit,GabrielNicolasAvellaneda/luvit-upstream,bsn069/luvit,sousoux/luvit,rjeli/luvit,DBarney/luvit,DBarney/luvit,luvit/luvit,GabrielNicolasAvellaneda/luvit-upstream,kaustavha/luvit,zhaozg/luvit,rjeli/luvit,sousoux/luvit,boundary/luvit,sousoux/luvit,boundary/luvit,sousoux/luvit,DBarney/luvit,bsn069/luvit,rjeli/luvit,zhaozg/luvit,sousoux/luvit,boundary/luvit