Spawn on Windows

[frankshearar]

def run_image_with_cmd(vm_name, arr_of_vm_args, image_name, cmd, timeout = 240)
  log(cmd)
  base_cmd = "#{vm_name} #{arr_of_vm_args.join(" ")} \"#{SRC}/target/#{image_name}.image\" #{as_relative_path(Pathname.new(cmd))}"
  case identify_os
    when "windows" then system(base_cmd)
  else
    log("spawning with timeout #{timeout.to_s} seconds: nice #{base_cmd}")
    pid = spawn("nice #{base_cmd}", err: STDERR, out: STDOUT)
    future {
      sleep(timeout.seconds)
      log("Killed command for exceeding allotted time: nice #{base_cmd}.")
      Process.kill('KILL', pid)
    }
    Process.wait(pid)
  end
end

Let's try spawn on Windows too, and just nice on non-Windows platforms.