fix build of APP=cardem on BOARD=simtrace

firmware/libboard/simtrace/source/board_simtrace.c

@@ -0,0 +1,17 @@
+/* SIMtrace specific application code */
+/* (C) 2017 by Harald Welte <laforge@gnumonks.org> */
+
+#include "board.h"
+#include "simtrace.h"
+#include "utils.h"
+#include "sim_switch.h"
+#include "osmocom/core/timer.h"
+#include "usb_buf.h"
+
+void board_exec_dbg_cmd(int ch)
+{
+}
+
+void board_main_top(void)
+{
+}