don't enforce flatpak protontricks on holoiso

[albert-softie]

i recently installed holoiso on my steam deck because i wanted to have access to proper package repos. unfortunately, despite being able to install and run protontricks from the AUR just fine, the installer script would error out during setup, telling me to try again after installing the flatpak version. after searching through the relevant scripts, i discovered that the error originates from check_dependencies.sh, which checks to see if non-flatpak protontricks is installed, as well as if source /etc/os-release; echo $ID (as run from protontricks.sh) returns steamos, which it always will because that's how holoiso is configured. i had to manually edit check_dependencies to intentionally break the steamos detection algorithm in order to continue with AUR protontricks. i believe there should be some way for the scripts to be able to detect whether the user is using stock steamos or holoiso, that way other holoiso users won't be forced to either install flatpak protontricks or edit the scripts as i did

[JackYansongLi]

I got the same error even I installed protontricks from discover app.

[rockerbacon]

Took a quick look at the os-release file for the original Steam OS 3 and HoloISO and it looks like the VARIANT_ID can be used to differentiate between the two. Steam OS 3 will set the variable to steamdeck and HoloISO should set it to snapshot<packaging date here>.