[conformal/btcgui] 81a722: use shell function instead of != operator

[Javed Khan]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcgui
  Commit: 81a722b765021b729ac9e8132da8b70b4a5cf23d
      
https://github.com/conformal/btcgui/commit/81a722b765021b729ac9e8132da8b70b4a5cf23d
  Author: Javed Khan <ja...@agiliq.com>
  Date:   2014-07-11 (Fri, 11 Jul 2014)

  Changed paths:
    M GNUmakefile

  Log Message:
  -----------
  use shell function instead of != operator