Remove Cygwin from blacklist in snapshot creation

Cygwin is still required for build on Windows. It was accidentally
blacklisted. Utils in cygwin used by third_party/WebKit build and
gyp uses cygwin for wrapping linux style commands on Windows.

Change-Id: Ifac069c67ebd1bef2f41618e7688d3b64028517b
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Reviewed-by: Andras Becsi <andras.becsi@digia.com>