reproduce:
        git remote add rust https://github.com/Rust-for-Linux/linux
        git fetch rust rust-next
        git checkout rust/rust-next
        b4 shazam https://lore.kernel.org/r/20240106065941.180796-1-wangrui@loongson.cn
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # install Sphinx 2.4.4
        make htmldocs