external libs look to be haphazardly chosen

[nieder]

This is on OS X/perl5.18.2:
Alien-sdl uses external libraries, but it seems to pick libraries inconsistently. It finds them all, but the versioning chosen is not consistent at all. This is from Alien/SDL/ConfigData.pm:

                       'ld_shared_libs' => [
                                             '/usr/lib/libpthread.dylib',
                                             '/usr/lib/libz.1.1.3.dylib',
                                             '/sw/lib/libjpeg.9.dylib',
                                             '/sw/lib/libtiff.5.dylib',
                                             '/sw/lib/libpng.dylib',
                                             '/sw/lib/libogg.0.dylib',
                                             '/sw/lib/libvorbis.0.dylib',
                                             '/sw/lib/libvorbisfile.3.dylib',
                                             '/sw/lib/libfreetype.dylib',
                                             '/sw/lib/libpangoft2-1.0.dylib',
                                             '/sw/lib/libpango-1.0.dylib',
                                             '/sw/lib/libgobject-2.0.0.dylib',
                                             '/sw/lib/libgmodule-2.0.0.dylib',
                                             '/sw/lib/libglib-2.0.0.dylib',
                                             '/sw/lib/libfontconfig.dylib',
                                             '/usr/lib/libexpat.1.5.2.dylib'
                                           ],

/sw is where I put my locally built external libraries (via Fink). Notice that some libraries get chosen with their unversioned SONAME (libpng.dylib), others get chosen with the single versioned SONAME (libtiff.5.dylib), and others use the fully versioned SONAME (libexpat.1.5.2.dylib). Unversioned and fully versioned dylibs are not guaranteed to always be present and the process should always use the versioning that matches the install_name of the dylib.
Also, the expat search is finding /usr/lib/libexpat.1.5.2.dylib, when there's a preferred /sw/lib/libexpat.1.6.5.dylib available (should be using /sw/lib/libexpat.1.dylib anyway).