/usr/lib/x86_64-linux-gnu/libgnatcoll.so is in libgnatcoll1.7-dev 1.7gpl2015-2+b3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgnatcoll.so.1.7
/usr/lib/x86_64-linux-gnu/libgnatcoll.so.1.7