reproduce (this is a W=1 build):
        # https://github.com/davidhildenbrand/linux/commit/b9189040ca4a05c8025ecff5b70a7895018d34e5
        git remote add davidhildenbrand https://github.com/davidhildenbrand/linux
        git fetch --no-tags davidhildenbrand hugetlb_unshare
        git checkout b9189040ca4a05c8025ecff5b70a7895018d34e5

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash mm/