Add a check for the bash shell to archdetect

init/eessi_archdetect.sh

@@ -1,4 +1,26 @@
 #!/usr/bin/env bash
+
+# Confirm the current shell is Bash >= 4
+check_bash() {
+    if [ -n "$BASH_VERSION" ]; then
+        # Extract the major version numbers
+        bash_version=$(echo "$BASH_VERSION" | grep -oP '^\d+\.\d+')
+        major_version=$(echo "$bash_version" | cut -d. -f1)
+
+        # Check if the major version is 4 or higher
+        if [ "$major_version" -ge 4 ]; then
+            return 0
+        else
+            echo "Error: This script must be run with Bash > 4, you have $BASH_VERSION." >&2
+            exit 1
+        fi
+    else
+        echo "Error: This script must be run with Bash." >&2
+        exit 1
+    fi
+}
+check_bash
+
 VERSION="1.1.0"
 
 # default log level: only emit warnings or errors