r2modman: fix launching Steam games

Patch r2modman to run "steam" instead of trying to directly run
"steam.sh" from the user's home directory.  This means it uses the NixOS
wrapper script, which runs Steam in the necessary FHS environment.

Fixes #240369

pkgs/games/r2modman/default.nix

@@ -28,6 +28,11 @@ stdenv.mkDerivation rec {
     hash = "sha256-CXitb/b2tvTfrkFrFv4KP4WdmMg+1sDtC/s2u5ezDfI=";
   };
 
+  patches = [
+    # Make it possible to launch Steam games from r2modman.
+    ./steam-launch-fix.patch
+  ];
+
   nativeBuildInputs = [
     yarn
     fixup_yarn_lock

pkgs/games/r2modman/steam-launch-fix.patch

@@ -0,0 +1,21 @@
+diff --git a/src/r2mm/launching/runners/linux/SteamGameRunner_Linux.ts b/src/r2mm/launching/runners/linux/SteamGameRunner_Linux.ts
+index ddee0e9..fc9ffca 100644
+--- a/src/r2mm/launching/runners/linux/SteamGameRunner_Linux.ts
++++ b/src/r2mm/launching/runners/linux/SteamGameRunner_Linux.ts
+@@ -61,15 +61,9 @@ export default class SteamGameRunner_Linux extends GameRunnerProvider {
+     async start(game: Game, args: string): Promise<void | R2Error> {
+ 
+         const settings = await ManagerSettings.getSingleton(game);
+-        const steamDir = await GameDirectoryResolverProvider.instance.getSteamDirectory();
+-        if(steamDir instanceof R2Error) {
+-            return steamDir;
+-        }
+-
+-        LoggerProvider.instance.Log(LogSeverity.INFO, `Steam directory is: ${steamDir}`);
+ 
+         try {
+-            const cmd = `"${steamDir}/steam.sh" -applaunch ${game.activePlatform.storeIdentifier} ${args} ${settings.getContext().gameSpecific.launchParameters}`;
++            const cmd = `steam -applaunch ${game.activePlatform.storeIdentifier} ${args} ${settings.getContext().gameSpecific.launchParameters}`;
+             LoggerProvider.instance.Log(LogSeverity.INFO, `Running command: ${cmd}`);
+             await exec(cmd);
+         } catch(err) {