/usr/lib/x86_64-linux-gnu/libSDL_stretch.so is in libsdl-stretch-dev 0.3.1-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libSDL_stretch-0.so.3.0.1
/usr/lib/x86_64-linux-gnu/libSDL_stretch-0.so.3.0.1