mmx: compile on MIPS for Loongson MMI optimizations

mmx: compile on MIPS for Loongson MMI optimizations

                             image               image16
           evolution   32.985 ->  29.667    27.314 ->  23.870
firefox-planet-gnome  197.982 -> 180.437   220.986 -> 205.057
gnome-system-monitor   48.482 ->  49.752    52.820 ->  49.528
  gnome-terminal-vim   60.799 ->  50.528    51.655 ->  44.131
      grads-heat-map    3.167 ->   3.181     3.328 ->   3.321
                gvim   38.646 ->  32.552    38.126 ->  34.453
       midori-zoomed   44.371 ->  43.338    28.860 ->  28.865
           ocitysmap   23.065 ->  18.057    23.046 ->  18.055
             poppler   43.676 ->  36.077    43.065 ->  36.090
  swfdec-giant-steps   20.166 ->  20.365    22.354 ->  16.578
      swfdec-youtube   31.502 ->  28.118    44.052 ->  41.771
   xfce4-terminal-a1   69.517 ->  51.288    62.225 ->  53.309