说明：  设计并实现Unix的“time”命令。“mytime”命令通过命令行参数接受要运行的程序，创建一个独立的进程来运行该程序，并记录程序运行的时间。
(Design and implement the Unix "time" command. "MyTime" command through the command-line parameter accepts a program to run, create a separate process to run the program, and record the time of the program is running.)