/usr/include/GNUstep/EOInterface/ is in libgnustep-dl2-dev 0.12.0-15.1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/GNUstep/EOInterface/EOActionAssociation.h
/usr/include/GNUstep/EOInterface/EOActionInsertionAssociation.h
/usr/include/GNUstep/EOInterface/EOAspectConnector.h
/usr/include/GNUstep/EOInterface/EOAssociation.h
/usr/include/GNUstep/EOInterface/EOColumnAssociation.h
/usr/include/GNUstep/EOInterface/EOComboBoxAssociation.h
/usr/include/GNUstep/EOInterface/EOControlAssociation.h
/usr/include/GNUstep/EOInterface/EODetailSelectionAssociation.h
/usr/include/GNUstep/EOInterface/EODisplayGroup.h
/usr/include/GNUstep/EOInterface/EOInterface.h
/usr/include/GNUstep/EOInterface/EOMasterCopyAssociation.h
/usr/include/GNUstep/EOInterface/EOMasterDetailAssociation.h
/usr/include/GNUstep/EOInterface/EOMatrixAssociation.h
/usr/include/GNUstep/EOInterface/EOPickTextAssociation.h
/usr/include/GNUstep/EOInterface/EOPopUpAssociation.h
/usr/include/GNUstep/EOInterface/EORadioMatrixAssociation.h
/usr/include/GNUstep/EOInterface/EORecursiveBrowserAssociation.h
/usr/include/GNUstep/EOInterface/EOTextAssociation.h