For the record, if you (or somebody else) encounters other strange build errors (particularly stuff about at_exit, or pthread not found), then you might want to try this:
Instead of installing cmake and gcc via conda, install them via your system. I’m doing this on ubuntu 16.04.
So my setup looks like:
sudo apt-get install g++ cmake
conda install numpy pyyaml mkl setuptools cffi       # notice g++ and cmake removed from here
This was mentioned, I think by Sean Naren on a warp-ctc build issue, but thought I might mention it here too.