link-rs.sh: use only -l options for library names
link-rs.sh: use only -l options for library names

pkg-config might also output -L options.

tomaka/glfw-rs,derekdreery/glfw-rs,servo/glfw-rs,PistonDevelopers/glfw-rs,bjz/glfw-rs,bvssvni/glfw-rs,derekdreery/glfw-rs,mneumann/glfw-rs,nstoddard/glfw-rs