reproduce (this is a W=1 build):
        git remote add drm-misc git://anongit.freedesktop.org/drm/drm-misc
        git fetch --no-tags drm-misc topic/rust-drm
        git checkout 536aa252b05694f74a7aca913fe25fe7e218df4f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash CLIPPY=1 rustdoc