### Maybe a NixOS config ###
I have to say I take a loooot of config from community.
And I didn't tell anyone I take it and I forget to label 
the code from who.

Sorry.

By the way, you can take it and needn't let me know. 

And I didn't make all into declarative. YOU MAY GET 
DIFFERENT RESULT.

Todo list:
    [x] C 语言环境搭建 注：虚拟机然后 SSH 进去搞的
    [] 学习 C 语言 flag：真的要完成 X_X