reproduce (this is a W=1 build):
        git remote add willy-pagecache git://git.infradead.org/users/willy/pagecache
        git fetch --no-tags willy-pagecache write-end
        git checkout a875d4f14434467d21cd6cbe9a5e2366d6405a85
        # 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 drivers/gpu/drm/i915/