KWSys 2021-03-30 (db93a594)

Code extracted from:

    https://gitlab.kitware.com/utils/kwsys.git

at commit db93a5948e331c8920ac701e35b2f7e283646cae (master).

Upstream Shortlog
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Lemures Lemniscati (2):
      9a6d6c54 Terminal: Avoid using Windows functions on Cygwin
      4c61b968 SystemTools::FileIsFullPath: Do not accept Windows paths on Cygwin