exit crash from SFML mismanagement of OAL context

SFML doesn't have a working, portable way of deinitializing the OpenAL
context it creates from playing sound files.  They have known about this
since 2011, as evidenced by
https://github.com/LaurentGomila/SFML/issues/30.  Fortunately, somebody in
the comments section found a quick fix.

Switch the order in which the SFML libraries are linked.