Another makefile $(build_exeext) patch for cygwin

[law@redhat.com]

  In message < A9E96A79C068D211A6A90000C07BDF0D88F3CB@crtsmail.corp.riotinto.org
>you write:
  > Another makefile $(build_exeext) patch for cygwin.  Partial bootstrap on
  > cygwin and bootstrap on irix.  Please apply if OK.
  > 
  > 
  > 2000-11-21  David Billinghurst  <David.Billinghurst@riotinto.com)
  > 
  > 	* Make-lang.in:  Add $(build_exeext) to f/fini target
Thanks.  Installed.
jeff