cmake-gui: Restore support for internationalization with Qt5 on Windows

Restore the logic removed by commit 035078d8 (cmake-gui: Remove
explicit locale setup, 2020-12-17, v3.20.0-rc1~205^2~6), but only with
Qt5 on Windows.  Leave a FIXME comment to support Qt6 later.

Fixes: #23562
Issue: #23565
41 jobs for !7303 with cmake-gui-locale in 24 minutes and 56 seconds (queued for 5 seconds)
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