reproduce (this is a W=1 build):
        # https://github.com/alexshi/linux/commit/7f684a3f36349d046c74e1ba46afb096a0cc2463
        git remote add alexshi https://github.com/alexshi/linux.git
        git fetch --no-tags alexshi isolation
        git checkout 7f684a3f36349d046c74e1ba46afb096a0cc2463
        # 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