Retroarch improvements (part 2)

[GeoffreyCoulaud]

The goal is to make it possible to import and start games from Steam RetroArch inside of Cartridges

[GeoffreyCoulaud]

(basically works, suspected to be broken in upstream)

[pbone64]

I'd like to add some info from my own testing:

Running a RetroArch game with xdg-open 'steam://rungameid/1118310//-L <core path> <rom path>' results in the steam "starting game" window opening and closing without RetroArch actually starting (I got the same result with URL encoded launch args). I was, however, able to have RetroArch launch into a game with steam -applaunch 1118310 -L '<core path>' '<rom path>'. It should be noted that launching steam games via this method doesn't bring up a "starting game" window, which could be considered either a positive or negative.

If issues with the xdg-open method are a blocker for this PR then this is a possible solution.

Tested on Fedora Budgie 39 with Cartridges 2.6.3 installed via flatpak.