This is a Visual Studio 2012+ extension which automatically triggers all T4 templates in your solution (or selected project for project-only builds) to be re-run before build.

Just build and install the template using the VSIX file, grab it from the Visual Studio gallery or do it the easy way and use the 'Extension & Updates' manager in Visual Studio 2012+.

By default, the template will run all of your T4 templates on build. If you want to turn off individual templates, you can do this by setting Run on build to false in the Properties window for any .tt file in your solution.