ci: setup a linux host

Sets up a linux host to prepare for a build.

ci/setup-linux.sh

+#!/bin/sh
+
+set -x
+
+apt-get update
+apt-get -y install build-essential pkg-config cmake openssl libssl-dev libssh2-1-dev libcurl4-gnutls-dev openssh-server
+
+mkdir -p /var/run/sshd