GetTargetsLocation: throw if not found

Throws a DirectoryNotFoundException if the build directory is not found.
Fixes dotnet#1733.

tools/dotnet-aspnet-codegenerator/Program.cs

@@ -297,21 +297,21 @@ private IProjectContext GetProjectInformation(string projectPath, string configu
 
  private string GetTargetsLocation()
  {
+ const string build = "build";
  var assembly = typeof(Program).GetTypeInfo().Assembly;
  var path = Path.GetDirectoryName(assembly.Location);
  // Crawl up from assembly location till we find 'build' directory.
  do
  {
- if (Directory.EnumerateDirectories(path, "build", SearchOption.TopDirectoryOnly).Any())
+ if (Directory.EnumerateDirectories(path, build, SearchOption.TopDirectoryOnly).Any())
  {
  return path;
  }
 
  path = Path.GetDirectoryName(path);
  } while (path != null);
 
-
- return string.Empty;
+ throw new DirectoryNotFoundException(string.Format(Resources .TargetDirectoryNotFound, build));
  }
 
  private int Build(ILogger logger, string projectPath, string configuration, string shortFramework, string buildBasePath)