RT-Thread/rt-thread: https://github.com/RT-Thread/rt-thread.git @ b204651517aa1840d778f2f6fcfdc40207cab753

Bernard Xiong b204651517 Merge pull request #4333 from mysterywolf/pthread		4 lat temu
..
sys	598aa86f75 move clock_time_to_tick to time.c	4 lat temu
SConscript	e927a53b41 精简exit abort system函数	4 lat temu
readme.md	d5f8830177 add newlib/dlib readme	5 lat temu
stdlib.c	263d856fa4 update	4 lat temu
termios.h	54143409ca 增加#include <rtconfig.h> 防止开启termios功能后报错	5 lat temu
time.c	598aa86f75 move clock_time_to_tick to time.c	4 lat temu
unistd.c	fa8e8ed31f add RTM_EXPORT label for unistd.c	4 lat temu

Attentions

This folder is "common" for armlibc newlibc and dlib. It's not "common" for minilibc.
If you want to add new .c files, please do not forget to fix SConscript file too. eg:
```
if GetDepend('RT_USING_POSIX') == False:
    SrcRemove(src, ['unistd.c'])
```