fix(cluster): return error code if destdir missing

Previously, the script only logged an error when the 'destdir' argument was
not provided, but did not exit with a non-zero status. This change ensures
the script returns 1 in such cases, allowing calling processes to detect
the failure.

Author: mkoura

cardano_node_tests/prepare_cluster_scripts.py

@@ -91,6 +91,8 @@ def main() -> int:
 
     if not args.dest_dir:
         LOGGER.error("The 'destdir' must be set.")
+        return 1
+
     destdir = pl.Path(args.dest_dir)
 
     testnet_variant = args.testnet_variant