Explicitly set the console output encoding in GetGrammar

We always want the output to be in UTF-8.

Author: jskeet

tools/GetGrammar/Program.cs

@@ -24,6 +24,7 @@
 
 using System;
 using System.IO;
+using System.Text;
 using System.Threading.Tasks;
 
 namespace ExtractGrammar
@@ -40,6 +41,8 @@ public static async Task Main(string[] args)
             using var inputFile = new StreamReader(args[0]);
             string section = "";
 
+            Console.OutputEncoding = Encoding.UTF8;
+
             while (await inputFile.ReadLineAsync() is string inputLine)
             {
                 if (inputLine.StartsWith("#"))