Add Shared Host MSI Authoring

Ideally in the project.json for the shared host we would just list the
actual package that holds the shared host, instead of all of
NetStandard.Library, but doing some leads to compliation errors, since
publish wants to include a compile step that has a generated
AssemblyAttributes file which references types like System.String.

scripts/dotnet-cli-build/PrepareTargets.cs

@@ -113,6 +113,7 @@ namespace Microsoft.DotNet.Cli.Build
             c.BuildContext["VersionBadge"] = Path.Combine(Dirs.Output, versionBadgeName);
 
             AddInstallerArtifactToContext(c, "dotnet", "Sdk");
+            AddInstallerArtifactToContext(c, "dotnet-host", "SharedHost");
 
             return c.Success();
         }