nsc: Fix build problem if gtk config store is disabled
gtk config store pulled in libdl.so for us, so things fail
to link of the config store isn't enabled. This makes nsc
pull in libdl itself when its enabled.
Raj Bhattacharjea (raj.b@gatech.edu)
Gustavo Carneiro (gjc@inescporto.pt, gjcarneiro@gmail.com)
Craig Dowell (craigdo@ee.washington.edu)
Tom Henderson (tomhend@u.washington.edu)
Joe Kopena (tjkopena@cs.drexel.edu)
Mathieu Lacage (mathieu.lacage@sophia.inria.fr)
Emmanuelle Laprise (emmmanuelle.laprise@bluekazoo.ca)
Federico Maguolo (maguolof@dei.unipd.it)
George F. Riley (riley@ece.gatech.edu)
Guillaume Vu-Brugier (gvubrugier@gmail.com)
Florian Westphal (fw@strlen.de)