reproduce (this is a W=1 build):
        # https://github.com/intel/tdx/commit/bbac4998cfb34da496646491038b03f501964cbd
        git remote add intel-tdx https://github.com/intel/tdx.git
        git fetch --no-tags intel-tdx kvm-upstream
        git checkout bbac4998cfb34da496646491038b03f501964cbd
        # 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