Installs shared objects for git subprojects/submodules in global $libdir
The new gtk-frdp and libovf-glib dependencies that were added as git subprojects/submodules lead to these shared objects being installed: /usr/lib64/libgtk-frdp-0.1.so /usr/lib64/libgovf-0.1.so
That's not nice because they should be private to gnome-boxes and not in the OS' global shared library namespace. We should either put them in a private sub-directory, or statically link them into the main binary.