Placate versions of ranlib which complain about empty files (Mac OS X 10.4)

src/main/dummy/SDL_dummy_main.c

@@ -11,5 +11,11 @@ main(int argc, char *argv[])
 }
 #else
 /* Nothing to do on this platform */
+int
+SDL_main_stub_symbol()
+{
+    return 0;
+}
 #endif
+
 /* vi: set ts=4 sw=4 expandtab: */