/usr/bin/gtk-update-icon-cache-3.0 is in libgtk-3-bin 3.4.2-0ubuntu0.9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../lib/x86_64-linux-gnu/libgtk-3-0/gtk-update-icon-cache-3.0
/usr/bin/../lib/x86_64-linux-gnu/libgtk-3-0/gtk-update-icon-cache-3.0