/lib/x86_64-linux-gnu/libc.so.6 is in libc6 2.24-11+deb9u4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libc-2.24.so
/lib/x86_64-linux-gnu/libc-2.24.so