/usr/share/doc/libgl1-mesa-swx11-dev/changelog.Debian.gz is in libgl1-mesa-swx11-dev 8.0.2-0ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libgl1-mesa-swx11-dev/../libosmesa6/changelog.Debian.gz