On OS X, only consider MacPorts and Darwin packages
On OS X, only consider MacPorts and Darwin packages

Previously, we collected all the packages for matching Darwin and then
all the packages matching MacPorts together. However, if there were no
MacPorts packages then we'd fall back to trying all packages, even if
we did have some Darwin packages.

gasche/0install,gasche/0install,0install/0install,bastianeicher/0install,0install/0install,bastianeicher/0install,gasche/0install,bastianeicher/0install,gasche/0install,0install/0install