mmap: Only use MAP_NOCACHE on platforms that support it.

That would be Darwin and some BSDs apparently

modules/access/mmap.c

@@ -136,7 +136,12 @@ static int Open (vlc_object_t *p_this)
     /* Autodetect mmap() support */
     if (st.st_size > 0)
     {
-        void *addr = mmap (NULL, 1, PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_NOCACHE, fd, 0);
+        int flags = MAP_PRIVATE;
+#if defined(MAP_NOCACHE)
+        flags |= MAP_NOCACHE;
+#endif
+
+        void *addr = mmap (NULL, 1, PROT_READ|PROT_WRITE, flags, fd, 0);
         if (addr != MAP_FAILED)
             munmap (addr, 1);
         else