Install sxs with the install-dotnet scripts (#124)

* Use dotnet-install scripts for proper sxs

* Update dotnet version in testing

* Error message cleanup

* SxS testing in the dotnet project

* Update package lock

* Test fixes

* Use proper environment variable

* Set dotnet root for windows

__tests__/sample-csproj/Program.cs

@@ -1,14 +1,15 @@
-using System;
-using Newtonsoft.Json;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
 
 namespace sample_csproj
 {
-    class Program
+    [TestClass]
+    public class Program
     {
-        static void Main(string[] args)
+        [TestMethod]
+        public void TestMethod1()
         {
-            var json = JsonConvert.SerializeObject(new[] {"Hello", "World!" });
-            Console.WriteLine(json);
+            Console.WriteLine("Hello, World!");
         }
     }
 }