# Pastebin 3YwfY8mX
rburton: this is my latest attempt.  I have tried the same function as do_install and do_install_append (without the addtask in the other cases):

inherit cmake systemd
...
do_install_systemd () {
    install -d ${D}${systemd_unitdir}/system/
    bbwarn("in install append: %s", ${SYSTEMD_SERVICE_${PN}-systemd-auto});
    for service_file_name in SYSTEMD_SERVICE_${PN}-systemd-auto; do
        install -m 0644 ${WORKDIR}/${service_file_name} ${D}${systemd_unitdir}/system/
        sed -i -e 's!@BINDIR@!${bindir}!g' ${D}${systemd_unitdir}/system/${service_file_name}
    done
    for service_file_name in SYSTEMD_SERVICE_${PN}-systemd-noauto; do
        install -m 0644 ${WORKDIR}/${service_file_name} ${D}${systemd_unitdir}/system/
        sed -i -e 's!@BINDIR@!${bindir}!g' ${D}${systemd_unitdir}/system/${service_file_name}
    done

addtask install_systemd after do_install before do_package