/usr/lib/x86_64-linux-gnu/libuim-custom.so is in libuim-dev 1:1.8.6+gh20180114.64e3173-2build2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libuim-custom.so.2.1.0
/usr/lib/x86_64-linux-gnu/libuim-custom.so.2.1.0