testing/cog: missing symlink?

@markand I was unable to start cog on armv7 wayland (wayfire) because it was looking for libWPEBackend-fdo-1.0.so which seems to exist in the libwpebackend-fdo-dev package but not the non-dev package that cog pulls in. I created a symlink with that name to /usr/lib/libWPEBackend-fdo-1.0.so.1.8.3 and then cog launched ok.