Replace condition of XCB::XFIXES from the 'XCB_XFIXES_FOUND' variable to 'TARGET XCB::XFIXES'. Fixes: QTBUG-89979 Change-Id: I77b8b4046dc6852ecb209d942ee94d864a35c378 Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>