The tag is present in Lintian version 2.104.318. That is the most recent version we know about.
The package installs shared libraries in a directory controlled by the dynamic library loader. Therefore, the package must trigger libc's "ldconfig" trigger to ensure the ldconfig cache is updated.
If the package is using debhelper,
automatically discover this and add the trigger itself.
Otherwise, please add
activate-noawait ldconfig to the
triggers file in the control member.
Note this tag may trigger for packages built with debhelper before version 9.20151004. In such case, a simple rebuild will often be sufficient to fix this issue.
Please refer to Debian Policy Manual section 8.1.1 and https://lists.debian.org/debian-devel/2015/08/msg00412.html for details.