feat: add contents about env setup on macOS

[werifu]

添加了macOS下实验环境的安装指南，已在M1 pro MacBook Pro 与 x86_64 MacBook Pro 下做过验证，均可通过 make testx 的测试。

[darionyaphet]

你的 Rust 什么版本？rustc 1.64.0 报错

error[E0463]: can't find crate for `core`
  |
  = note: the `riscv64gc-unknown-none-elf` target may not be installed
  = help: consider downloading the target with `rustup target add riscv64gc-unknown-none-elf`

error[E0463]: can't find crate for `compiler_builtins`

For more information about this error, try `rustc --explain E0463`.
error: could not compile `cfg-if` due to 2 previous errors
warning: build failed, waiting for other jobs to finish...
make: *** [kernel] Error 101

[werifu]

@darionyaphet 我是 1.62.1，上面这个报错看着是没装 rv 的 target ，你试过 rustup target add riscv64gc-unknown-none-elf 了吗

[darionyaphet]

试过 但并没效果 还是这个错误？ 请问我需要清理一下吗？