Description of problem: mozilla-plugin.pc does not define libdir, while xulrunner-plugin.pc does. This causes problems building gecko-mediaplayer. Version-Release number of selected component (if applicable): 1.9-0.beta1.3.fc9
fixed in xulrunner-1.9-0.beta1.4.fc9. But you should use xulrunner-plugin.pc, anyway.
Yeah, we should probably get rid of mozilla-*.pc