Propose a dead simple way to show systemd configuration

while the local systemd version is too low to support `cat-config` function.

install-release.sh

@@ -34,6 +34,8 @@ systemd_cat_config() {
   if systemd-analyze --help | grep -qw 'cat-config'; then
     systemd-analyze --no-pager cat-config "$@"
   else
+    echo
+    cat "$@" "$1".d/*
     echo "${red}warning: ${green}The systemd version on the current operating system is too low."
     echo "${red}warning: ${green}Please consider to upgrade the systemd or the operating system.${reset}"
   fi