Psvita core compilation problem

I have installed the vitasdk and msys, which I use./libretro-build-vita.sh fceumm command is compiled with fceumm_libretro.a instead of fceumm_libretro.self. I changed fceumm_libretro.a to fceumm_libretro.self into vita, and the emu went wrong. How do I compile it to fceumm_libretro.Self? thanks