Implement
- userland build in nix, with cross platform support and
non-previleged disk gen
- qemu start command in nix
- nix develop envrionment for make kernel
- document build environment defined by nix
Next Steps
- 减小rootfs占用nix store的体积
- deb包的打包兼容用的函数
- 更加灵活的构建依赖注入
- 保留先前系统内修改的内容
- nix rootfs build与qemu启动适配 vnc模式
- 适配 riscv64 构建
- Arm MacOS上的开发兼容