/usr/lib/gnash/libgnashamf.so is in gnash-dev 0.8.11~git20160109-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gnash/libgnashamf-0.8.11.so
/usr/lib/gnash/libgnashamf-0.8.11.so