/usr/lib/x86_64-linux-gnu/libicuio.so is in libicu-dev 57.1-6+deb9u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libicuio.so.57.1
/usr/lib/x86_64-linux-gnu/libicuio.so.57.1