I would instead of make install with a DESTDIR setting.
right after "make -j4" # The "-j4" can be dropped btw,
mkdir PKGIf you ever need to uninstall, you can safely do removepkg kernel_backports
make DESTDIR=$PWD/PKG install
makepkg -l y -c n ../kernel_backports-<your_version_here>-i586-1vl70.txz