sodepends: Read DT_RUNPATH too

DT_RPATH is deprecated and ignored if DT_RUNPATH present. It fixes detecting internal library dependencies.

E.g. /usr/bin/gnome-boxes contains a DT_RUNPATH /usr/lib/gnome-boxes and tries to load the libgovf-0.1.so library. Without this patch, namcap shows a warning:

gnome-boxes W: Referenced library 'libgovf-0.1.so' is an uninstalled dependency

With this patch, the internal dependency is detected properly, and no warning shown.