Main loop is blocked in the libgomp.so library

[lc-soft]

Describe the bug
When a new main loop is created and run in the event handler, the main thread will block in libgomp.so.

To Reproduce
Steps to reproduce the behavior:

1. Run test
2. Waiting for test results

Expected behavior
The main thread is not blocked.

Screenshots

Environment (please complete the following information):

• LCUI version: develop branch
• Build tools: gcc
• OS and version: Ubuntu 18.04.3 LTS

Additional context

LCUI/test/test_mainloop.c

Lines 42 to 74 in 3758e21

	static void ObserverThread(void *arg)
	{
	LCUI_BOOL exited = *((LCUI_BOOL*)arg);
	LCUI_MSleep(100);
	it_b("main loop should exit after 50ms", exited, TRUE);
	if (!exited) {
	exit(-print_test_result());
	return;
	}
	LCUIThread_Exit(NULL);
	}
	void test_mainloop(void)
	{
	static LCUI_BOOL exited;
	LCUI_Thread tid;
	LCUI_Widget root, btn;
	LCUI_Init();
	exited = FALSE;
	btn = LCUIWidget_New("button");
	root = LCUIWidget_GetRoot();
	Button_SetText(btn, "button");
	Widget_BindEvent(btn, "click", OnBtnClick, NULL, NULL);
	Widget_Append(root, btn);
	LCUIThread_Create(&tid, ObserverThread, &exited);
	LCUI_SetTimeout(100, OnTriggerBtnClick, btn);
	LCUI_Main();
	exited = TRUE;
	LCUIThread_Join(tid, NULL);
	}