/usr/lib/libreoffice/share/uno_packages/cache is in libreoffice-core 1:5.2.7-1+deb9u5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /var/spool/libreoffice/uno_packages/cache
/var/spool/libreoffice/uno_packages/cache