exclude errorSource from call to Environment.FailFast on Unix

Signed-off-by: dotnet-bot <[email protected]>

Author: sywhang

src/mscorlib/shared/System/Diagnostics/Debug.Unix.cs

@@ -21,8 +21,10 @@ private static void ShowDialog(string stackTrace, string message, string detailM
                 // In Core, we do not show a dialog.
                 // Fail in order to avoid anyone catching an exception and masking
                 // an assert failure.
+
+                // We can safely ignore errorSource since it's a CoreCLR specific argument for distinguishing calls from Debug.Assert and Environment.FailFast
                 var ex = new DebugAssertException(message, detailMessage, stackTrace);
-                Environment.FailFast(ex.Message, ex, errorSource);
+                Environment.FailFast(ex.Message, ex);
             }
         }