/usr/share/doc/libclang-common-6.0-dev/NEWS.Debian.gz is in libclang-common-6.0-dev 1:6.0-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libclang-common-6.0-dev/../libllvm6.0/NEWS.Debian.gz