Create a wine prefix per user

[Maykin-99]

Fixes #4820 by setting the base directory of CompatData from steamapps/compatdata/<steamid>/ to steamapps/compatdata/<steamid>/<userid>/ (I'm honestly surprised that it worked without a hitch).

The only issue is that the old files still exist.
Ideally we would move them to the new path.
I assume that would belong in upgrade_pfx? Or is it even necessary?

[VannTen]

How could we make this progress forward ?
I just got it by the exact same problem when trying to make family sharing work.

[Nomz420]

Could someone look into this? This fix would prove really useful for us.

[CorruptComputer]

Does this break Steam Cloud save backups? Might need some coordination with the Steam folks to make sure this doesn't break existing save backups.

[jessecambon]

+1 also related to ValveSoftware/steam-for-linux#3942

[etyarews]

+1 This would fix so many issues

[eilimrib]

Please. This is giving me nightmare having to recompile Proton just to share my games with my wife.

[Damglador]

@eilimrib you don't have to compile it. Since it's a change in a simple python file, you can just do the same change in already installed Proton version

[Damglador]

Perhaps it's better to store prefixes in the local compatdata? Because in case user1 with 1000 and user2 with 1001 on the first system won't get swapped prefixes on a system where user1 is 1001 and user2 is 1000

[shaft8472]

So, I found that this is the reason why I cannot let my two sons make use of the same gamedata as my account. Seems like a simple fix.

[Damglador]

I would do this as a personal patch:

self.base_dir = os.path.join(os.environ["STEAM_COMPAT_CLIENT_INSTALL_PATH"], "steamapps", "compatdata", os.environ["SteamAppId"]) + "/"

Or, from my understanding, Steam just could supply a local compatdata directory in STEAM_COMPAT_DATA_PATH variable, instead of the one in portable library.