This file is indexed.

/usr/lib/x86_64-linux-gnu/libgtkmm-3.0.so is in libgtkmm-3.0-dev 3.14.0-1.

This file is owned by root:root, with mode 0o777.

It is a symlink to /usr/lib/x86_64-linux-gnu/libgtkmm-3.0.so.1.1.0