/usr/share/gtk-doc/html/libvirt is in libvirt-doc 4.0.0-1ubuntu8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gtk-doc/html/../../doc/libvirt-doc/devhelp
/usr/share/gtk-doc/html/../../doc/libvirt-doc/devhelp