[devel] Add a Vagrantfile.
[devel] Add a Vagrantfile.

 - This is just a minimal file for bringing up a viable Ubuntu 16.04 for llbuild
   development.

apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild