/usr/lib/gcc/x86_64-linux-gnu/6/libgij.so is in gcj-6-jdk 6.3.0-18+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libgij.so.17
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libgij.so.17