reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/commit/?id=bf20f42e7ef8a03b1df8aca27e5159b87f7d40ea
        git remote add rppt https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git
        git fetch --no-tags rppt uffd+guestmemfd/v1
        git checkout bf20f42e7ef8a03b1df8aca27e5159b87f7d40ea

        # 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