i see in some extensions there is an icon-theme.cache file which might have huge sizes depending on the extensions installed at the time of packaging
a special care must be taken when using touch /tmp/mark find -newer /tmp/mark .... method for collecting installed files
when issuing the command sudo make install not just files installed but also some specific commands are called such as gtk-update-icon-cache, update-desktop-database, update-mime-database or gconf schemas install
to me the best place to handle this kind of post install commands is the tce.installed script
so whenever DESTDIR or INSTALL_ROOT is available use it and put these commands in your tce.installed script