docs: public String hashSystemEnv() {
          List<String> system = new ArrayList<String>();
          for (Entry<Object, Object> el : System.getProperties().entrySet()) {
              system.add(el.getKey() + " " + el.getValue());
          }
  
          Map<String, String> env = System.getenv();
          for (Entry<String, String> el : env.entrySet()) {
              system.add(el.getKey() + " " + el.getValue());
          }
          Collections.sort(system);
  
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          try {
              DataOutputStream dos = new DataOutputStream(baos);
              for (String s : system) {
                  dos.write(s.getBytes());
              }
          } catch (IOException ex) {
              // never
          }
          return hashByteArray(baos.toByteArray());
      }