/usr/lib/R/site-library/RGtk2/include/ is in r-cran-rgtk2 2.20.31-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/R/site-library/RGtk2/include/RGtk2/
/usr/lib/R/site-library/RGtk2/include/RGtk2/RSCommon.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/atk.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/atkClassImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/atkClasses.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/atkImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/atkUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/atkUserFuncs.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/cairo-enums.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/cairo.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/cairoImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/cairoUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/cairoUserFuncs.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdk.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdkClassImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdkClasses.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdkImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdkUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gdkUserFuncs.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gio.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gioClassImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gioClasses.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gioImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gioUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gioUserFuncs.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gobject.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gobjectImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtk.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtkClassImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtkClasses.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtkImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtkUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/gtkUserFuncs.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/pango.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/pangoClassImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/pangoClasses.h
/usr/lib/R/site-library/RGtk2/include/RGtk2/pangoImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/pangoUserFuncImports.c
/usr/lib/R/site-library/RGtk2/include/RGtk2/pangoUserFuncs.h