steam: Add extraArgs to prepend arguments to Steam

The steam launcher script in SteamOS 3 always prepends `-steamdeck`
to ensure the correct client version is used. This argument enables
us to replicate the setup in NixOS.

Changed files
+2 -1
pkgs
games
steam
+2 -1
pkgs/games/steam/fhsenv.nix
···
, extraPkgs ? pkgs: [ ] # extra packages to add to targetPkgs
, extraLibraries ? pkgs: [ ] # extra packages to add to multiPkgs
, extraProfile ? "" # string to append to profile
+
, extraArgs ? "" # arguments to always pass to steam
, runtimeOnly ? false
, runtimeShell
, stdenv
···
${exportLDPath}
${fixBootstrap}
-
exec steam "$@"
+
exec steam ${extraArgs} "$@"
'';
inherit (steam) meta;