RT-Thread-Studio/sdk-rt-thread-source-code: https://github.com/RT-Thread-Studio/sdk-rt-thread-source-code.git @ 4.0.3

yaxing.chen c0257098b9 release rt-thread v4.0.3		4 lat temu
..
sys	c0257098b9 release rt-thread v4.0.3	4 lat temu
SConscript	c0257098b9 release rt-thread v4.0.3	4 lat temu
readme.md	c0257098b9 release rt-thread v4.0.3	4 lat temu
termios.h	c0257098b9 release rt-thread v4.0.3	4 lat temu
time.c	c0257098b9 release rt-thread v4.0.3	4 lat temu
unistd.c	c0257098b9 release rt-thread v4.0.3	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'])
```