ensure .desktop files are executable

before, for any non-root installation, most of them did not work, as not installed executable

you will get this message on the console

kf.config.core: Access to ' "/home/cullmann/projects/kde/usr/share/kf5/kmoretools/presets-kmoretools/gitk.kmt-edition.desktop" ' denied, not owned by root, executable flag not set.