Fix multiple instances of a game being allowed to start concurrently

[peppy]

Regressed with #6442. Closes ppy/osu#31072.

Was not visible in test coverage because as per the inline comment, this is an exceptional case where two different processes bind.

I'm not sure how to add test coverage for this, but I have tested manually on both windows and macOS.

Can test using this:

diff --git a/SampleGame.Desktop/Program.cs b/SampleGame.Desktop/Program.cs
index 4756edbaa..ae5075535 100644
--- a/SampleGame.Desktop/Program.cs
+++ b/SampleGame.Desktop/Program.cs
@@ -12,9 +12,17 @@ public static class Program
         [STAThread]
         public static void Main(string[] args)
         {
-            using (GameHost host = Host.GetSuitableDesktopHost(@"sample-game"))
+            using (GameHost host = Host.GetSuitableDesktopHost(@"sample-game", new HostOptions
+                   {
+                       IPCPipeName = "wang"
+                   }))
             using (Game game = new SampleGameGame())
+            {
+                if (host.IsPrimaryInstance)
+                    return;
+
                 host.Run(game);
+            }
         }
     }
 }

[bdach]

Not sure how it happened but your test diff is a little backwards (the IsPrimaryInstance check should be negated shouldn't it?)

Other than that tested on linux (including testing with a local game checkout) and things seem to be working fine, so 👍 Not checking windows (or mac, obviously 😅)

[peppy]

Not sure how it happened but your test diff is a little backwards (the IsPrimaryInstance check should be negated shouldn't it?)

Yeah I rewrote it locally for the sake of the PR description because copy-paste to my windows testing machine was not working. Safe to say it was the correct negation when I actually tested.