/usr/lib/x86_64-linux-gnu/libgcroots.so is in libgcroots-dev 0.8.5-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgcroots.so.0.1.0
/usr/lib/x86_64-linux-gnu/libgcroots.so.0.1.0