/usr/share/doc/valac-0.18-dbg/changelog.Debian.gz is in valac-0.18-dbg 0.18.1-0ubuntu11.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/valac-0.18-dbg/../libvala-0.18-0/changelog.Debian.gz