ilspycmd: route update-check messages to stderr

stdout is the data channel: --resource may be writing a binary payload to
it. Update-check notices on stdout would tail-append to the binary stream
and corrupt extracted files. Move them to stderr (npm/cargo/pip
convention) so meta-output stays out of the data path.

Author: siegfriedpammer

ICSharpCode.ILSpyCmd/IlspyCmdProgram.cs

@@ -276,8 +276,8 @@ private async Task<int> OnExecuteAsync(CommandLineApplication app)
 					var checkResult = await updateCheckTask;
 					if (null != checkResult && checkResult.UpdateRecommendation)
 					{
-						Console.WriteLine("You are not using the latest version of the tool, please update.");
-						Console.WriteLine($"Latest version is '{checkResult.LatestVersion}' (yours is '{checkResult.RunningVersion}')");
+						app.Error.WriteLine("You are not using the latest version of the tool, please update.");
+						app.Error.WriteLine($"Latest version is '{checkResult.LatestVersion}' (yours is '{checkResult.RunningVersion}')");
 					}
 				}
 			}