Build verification automation test tool

We are automating our build verification tests.Our build includes multiple components including UI , back-end components and also web services. We use different test automation tools like Selenium web driver ,Spec flow and custom scripts for component testing. We are looking for a tool (preferably open source) which will facilitate end to end Build verification testing which will in-turn call the automation scripts from Selenium web-driver or from spec-flow. Any pointers on this is appreciated.