FreeBSD port for Tensorflow 1.15

This provides an easy to use copy of science/libtensorflow1 until the port is committed to the repository.

You can follow the port progress in bug 260694

Usage

cd /usr/ports/science
git clone https://github.com/psa/libtensorflow1-freebsd-port libtensorflow1
cd libtensorflow1
make package

This takes a long time to build (~90 minutes with 4 Xeon E31275 @ 3.40GHz cores) and 8 GiB of RAM.