libtool: allow passing full file paths as deps
libtool: allow passing full file paths as deps

Allows having a library e.g. plugin depend on another library in a
different directory.

fluendo/cerbero,GStreamer/cerbero,fluendo/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero,atsushieno/cerbero,atsushieno/cerbero,nirbheek/cerbero,fluendo/cerbero,GStreamer/cerbero,atsushieno/cerbero,GStreamer/cerbero,fluendo/cerbero,fluendo/cerbero,GStreamer/cerbero,nirbheek/cerbero,GStreamer/cerbero,nirbheek/cerbero