calamares-finish-oem.desktop is untrusted

[ԜаӀtеr Ⅼарсһуnѕkі]

The UX when finishing/personalizing an OEM install of Lubuntu (and most likely, Kubuntu and Ubuntu Unity) is a little substandard because:
 1. The Desktop Entry on the Desktop to start the process is untrusted
 2. The default preferences prompt the user before executing

The prompt by default includes three options:
 1. Open
 2. Execute
 3. Cancel

The difference between open and execute is not immediately obvious to everyone. Should they choose the first option (open) it opens in the text editor (Featherpad) which is *definitely* not what the user wants.

So, the solution is rather simple:
gio set calamares-finish-oem.desktop metadata::trusted true

This needs to be done before pcmanfm-qt is started or pcmanfm-qt needs to be restarted for this change to be picked up.

This should happen in calamares-oemprep.sh but it needs testing.