rubygems: fix install location
rubygems: fix install location

Don't install into local/... but in the location where all other gems
would be found.  At the same time, fix some inefficiencies, and
fragilities.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb