def ensure_headers
      missing = missing_headers
      return if missing.size == 0

      message = "Compilation cannot proceed as the following header files are missing:\n" + missing.join("\n") 
      raise Error.new(message)
    end
def ensure_headers
      missing = missing_headers
      return if missing.size == 0

      message = "Compilation cannot proceed as the following header files are missing:\n" + missing.join("\n") 
      raise Error.new(message)
    end
Raises an error if there are missing headers