Use _NEWLIB_VERSION macro to detect newlib.

ports/dosbox/nacl.patch

 diff --git a/include/setup.h b/include/setup.h
 index db75ada..f52b840 100644
 --- a/include/setup.h
 +++ b/include/setup.h
 @@ -21,6 +21,8 @@
  #ifndef DOSBOX_SETUP_H
  #define DOSBOX_SETUP_H
  
 +#include <stdio.h>
 +
@@ skipping 165 matching lines @@
 +#ifndef __native_client__
 +               |SDL_INIT_CDROM  /* nacl-SDL is not built with CDROM */
 +#endif  /* __native_client__ */
                 |SDL_INIT_NOPARACHUTE
                 ) < 0 ) E_Exit("Can't init SDL %s",SDL_GetError());
         sdl.inited = true;
 @@ -1899,6 +1902,22 @@ int main(int argc, char* argv[]) {
         return 0;
  }
  
-+#if defined(__native_client__) && !defined(__GLIBC__)
++#if defined(__native_client__) && defined(_NEWLIB_VERSION)
 +#include <libgen.h>
 +#include <assert.h>
 +
 +// Horrible hack to ensure that _execve is pulled out of libnosys.a
 +// TODO(sbc): Remove this once libnosys is rolled in libnacl
 +extern "C" void* _execve;
 +void* foo = (void*)_execve;
 +
 +char *dirname(char *path) {
 +  fprintf(stderr, "ERROR: %s is not implemented\n", __func__);
 +  assert(0);
 +  return NULL;
 +}
 +#endif
 +
  void GFX_GetSize(int &width, int &height, bool &fullscreen) {
         width = sdl.draw.width;
         height = sdl.draw.height;