protobuf/kokoro/linux/prepare_build_linux_rc

#!/bin/bash

# Source this rc script to prepare the environment for Linux builds

# Set up dotnet
sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/dotnet-release/ trusty main" > /etc/apt/sources.list.d/dotnetdev.list'
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 417A0893
sudo apt-get update
sudo apt-get install -y dotnet-dev-1.0.4