reproduce:
        # https://github.com/gourryinverse/linux/commit/64636b7d457b68054d7a759c4a688476a22044cb
        git remote add gourryinverse https://github.com/gourryinverse/linux
        git fetch --no-tags gourryinverse djhacks
        git checkout 64636b7d457b68054d7a759c4a688476a22044cb
        make menuconfig
        # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
        # pip install -r Documentation/sphinx/requirements.txt
        make htmldocs