/usr/lib/x86_64-linux-gnu/libopencv_stitching.so is in libopencv-stitching-dev 2.4.9.1+dfsg-1.5ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libopencv_stitching.so.2.4