autoconf: ./configure fails on cygwin for crosstool-ng-1.24.0

Hello,

I tried to run ./configure on the package crosstool-ng-1.24.0 under cygwin64
and it fails.

Here is the output:
   ./configure: This script requires a shell more modern than all
   ./configure: the shells that I found on your system.
   ./configure: Please tell [email protected] and
   ./configure: [email protected] about your system, including
   ./configure: any error possibly output before this message. Then
   ./configure: install a modern shell, or manually run the script
   ./configure: under such a shell if you do have one.

The shell is bash:
   $ echo $SHELL
   /bin/bash

Bash version:
   $ $SHELL --version
   GNU bash, Version 4.4.12(3)-release (x86_64-unknown-cygwin)
   Copyright (C) 2016 Free Software Foundation, Inc.
   Lizenz GPLv3+: GNU GPL Version 3 oder jünger
http://gnu.org/licenses/gpl.html

   Dies ist freie Software. Sie darf verändert und verteilt werden.
   Es wird keine Garantie gewährt, soweit das Gesetz es zulässt.

Is there anything I can do to solve the problem?
If I have to provide more information I'll gladly do.

Thank you in advance.

Best regards,
Philipp