Only check SELinux states if "getenforce" command exists

- Currently, if the SELinux config file exists, installed SELinux is assumed.
- But removing e.g. an APT package via "apt-get remove" leaves config files in place, or they could be present for other reasons.
- If the getenforce command is not present but the config file is, currently the installer exists without error message when calling getenforce due to "set -e".
- With this change, the presence of getenforce command is checked first. If it is not present, selinux-utils is not installed, which is a core part of SELinux, pulled in by selinux-basics as well. So it can be assumed that no SELinux is active if this command is missing.

Signed-off-by: MichaIng <micha@dietpi.com>

automated install/basic-install.sh

@@ -1980,9 +1980,9 @@ checkSelinux() {
     local DEFAULT_SELINUX
     local CURRENT_SELINUX
     local SELINUX_ENFORCING=0
-    # Check if a SELinux configuration file exists
-    if [[ -f /etc/selinux/config ]]; then
-        # If a SELinux configuration file was found, check the default SELinux mode.
+    # Check for SELinux configuration file and getenforce command
+    if [[ -f /etc/selinux/config ]] && command -v getenforce &> /dev/null; then
+        # Check the default SELinux mode
         DEFAULT_SELINUX=$(awk -F= '/^SELINUX=/ {print $2}' /etc/selinux/config)
         case "${DEFAULT_SELINUX,,}" in
             enforcing)