ffmpeg: fix passlogfile regression

ffmpeg.c

@@ -4378,7 +4378,11 @@ static void log_callback_null(void* ptr, int level, const char* fmt, va_list vl)
 static int opt_passlogfile(const char *opt, const char *arg)
 {
     pass_logfilename_prefix = arg;
+#if CONFIG_LIBX264_ENCODER
     return opt_default("passlogfile", arg);
+#else
+    return 0;
+#endif
 }
 
 static const OptionDef options[] = {