Disable debuger code if not enabled

Observed build issue on TizenRT:

    iotjs.c:58: undefined reference to `jerryx_debugger_tcp_create'
    iotjs.c:59: undefined reference to `jerryx_debugger_ws_create'
    iotjs.c:58: undefined reference to `jerryx_debugger_after_connect'

Change-Id: Id88c745c9712f6f620bbd200f493397572174ce6
Signed-off-by: Philippe Coval <p.coval@samsung.com>

src/iotjs.c

@@ -55,9 +55,10 @@ static bool jerry_initialize(iotjs_environment_t* env) {
 
   if (iotjs_environment_config(env)->debugger != NULL) {
     uint16_t port = iotjs_environment_config(env)->debugger->port;
+#ifdef JERRY_DEBUGGER
     jerryx_debugger_after_connect(jerryx_debugger_tcp_create(port) &&
                                   jerryx_debugger_ws_create());
-
+#endif
     if (!jerry_debugger_is_connected()) {
       DLOG("jerry debugger connection failed");
       return false;
@@ -66,6 +67,7 @@ static bool jerry_initialize(iotjs_environment_t* env) {
     jerry_debugger_continue();
   }
 
+
   // Set magic strings.
   iotjs_register_jerry_magic_string();