/usr/include/x86_64-linux-gnu/qt5/QtHelp/ is in qttools5-dev 5.5.1-3build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpContentItem
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpContentModel
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpContentWidget
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpEngine
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpEngineCore
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpGlobal
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpIndexModel
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpIndexWidget
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpSearchEngine
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpSearchQuery
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpSearchQueryWidget
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QHelpSearchResultWidget
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QtHelp
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QtHelpDepends
/usr/include/x86_64-linux-gnu/qt5/QtHelp/QtHelpVersion
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelp_global.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpcontentwidget.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpengine.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpenginecore.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpindexwidget.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpsearchengine.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpsearchquerywidget.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qhelpsearchresultwidget.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/qthelpversion.h