Print the last line twice when running C program
after i press `SPC l r` to run my C program，if thte last printf doesn't print a new line，it will be printed twic：

![bug](https://images.gitee.com/uploads/images/2021/0907/114315_fe385e77_7775293.png "屏幕截图.png")
（i write only one "Hello World.", but it finally print two）

if i add the `\n`, it will be right：
![image](https://user-images.githubusercontent.com/44550791/132303879-f128fa6d-ef49-48b6-9434-027cc6f4640c.png)

also all right to run `exe` directly in cmd. it shoud not be my gcc's problem：
![输入图片说明](https://images.gitee.com/uploads/images/2021/0907/114816_87fb22c1_7775293.png "屏幕截图.png")

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also print twice using `fprintf`
![image](https://user-images.githubusercontent.com/44550791/132303622-5d8d4e0e-a1ca-427d-998d-bf63198c7e5d.png)
