/usr/include/KGantt/ is in libkgantt-dev 2.6.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KGantt/KGanttAbstractGrid
/usr/include/KGantt/KGanttAbstractRowController
/usr/include/KGantt/KGanttConstraint
/usr/include/KGantt/KGanttConstraintGraphicsItem
/usr/include/KGantt/KGanttConstraintModel
/usr/include/KGantt/KGanttConstraintProxy
/usr/include/KGantt/KGanttDateTimeGrid
/usr/include/KGantt/KGanttForwardingProxyModel
/usr/include/KGantt/KGanttGlobal
/usr/include/KGantt/KGanttGraphicsItem
/usr/include/KGantt/KGanttGraphicsScene
/usr/include/KGantt/KGanttGraphicsView
/usr/include/KGantt/KGanttItemDelegate
/usr/include/KGantt/KGanttLegend
/usr/include/KGantt/KGanttListViewRowController
/usr/include/KGantt/KGanttProxyModel
/usr/include/KGantt/KGanttStyleOptionGanttItem
/usr/include/KGantt/KGanttSummaryHandlingProxyModel
/usr/include/KGantt/KGanttTreeViewRowController
/usr/include/KGantt/KGanttView
/usr/include/KGantt/kgantt_export.h
/usr/include/KGantt/kganttabstractgrid.h
/usr/include/KGantt/kganttabstractrowcontroller.h
/usr/include/KGantt/kganttconstraint.h
/usr/include/KGantt/kganttconstraintgraphicsitem.h
/usr/include/KGantt/kganttconstraintmodel.h
/usr/include/KGantt/kganttconstraintproxy.h
/usr/include/KGantt/kganttdatetimegrid.h
/usr/include/KGantt/kganttforwardingproxymodel.h
/usr/include/KGantt/kganttglobal.h
/usr/include/KGantt/kganttgraphicsitem.h
/usr/include/KGantt/kganttgraphicsscene.h
/usr/include/KGantt/kganttgraphicsview.h
/usr/include/KGantt/kganttitemdelegate.h
/usr/include/KGantt/kganttlegend.h
/usr/include/KGantt/kganttlistviewrowcontroller.h
/usr/include/KGantt/kganttproxymodel.h
/usr/include/KGantt/kganttstyleoptionganttitem.h
/usr/include/KGantt/kganttsummaryhandlingproxymodel.h
/usr/include/KGantt/kgantttreeviewrowcontroller.h
/usr/include/KGantt/kganttview.h