TBBs can't be built with LXC on Ubuntu 14.04
Quoting from https://lists.torproject.org/pipermail/tbb-dev/2014-June/000078.html
What I see i[s] that commands such as the following (from gbuild) do not receive the input from stdin, so they hang waiting for input:
system! "on-target setarch #{@arches[arch]} bash < target-bin/init-build.sh"
Maybe lxc-start has been changed to re-attach stdin somewhere else?