Mod: Add util functions
Mod: Add util functions

- `_os` help to detect operator system
- `_exec` exec command

JeeLiu/fir-cli,yunheli/fir-cli,agoodtest/fir-cli,noname007/fir-cli,shengwen1994/fir-cli,jonesgithub/fir-cli,FIRHQ/fir-cli,yunheli/fir-cli,FIRHQ/fir-cli,agoodtest/fir-cli