/usr/include/x86_64-linux-gnu/qt5/QtHelp/ is in qttools5-private-dev 5.5.1-3build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qclucenefieldnames_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpcollectionhandler_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpdatainterface_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpdbreader_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpengine_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpgenerator_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpprojectdata_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindex_default_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindexreader_clucene_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindexreader_default_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindexreader_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindexwriter_clucene_p.h
/usr/include/x86_64-linux-gnu/qt5/QtHelp/5.5.1/QtHelp/private/qhelpsearchindexwriter_default_p.h