The flite plugin for QtSpeech wasn't tested on CI as the development
files weren't installed.
Pick-to: 6.8 6.9 6.10
Change-Id: Ieefe42f67009b99cc95f54567f224972d12c1538
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Tim Blechmann <tim.blechmann@qt.io>