Log Message:
libnbcompat: Convert to a proper package.

Building this inline meant an excessive number of copies were built
during bootstrap, one for every package that required it.  Now only
one package is built, significantly reducing bootstrap time.

From Jonathan Perkin <jperkin@smartos.org>
via drecklypkg commit b671d8cd0be775fe2245d1cb5ba402f17ae95e94