/usr/lib/x86_64-linux-gnu/libswscale.so is in libswscale-dev 7:3.2.12-1~deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libswscale.so.4.2.100
/usr/lib/x86_64-linux-gnu/libswscale.so.4.2.100