gitlab runner 优化

修改镜像拉取策略

修改配置文件：/etc/gitlab-runner/config.toml 在对应 runner 节点下添加 pull_policy = "if-not-present" 就可以了

[[runners]]
  name = "Android Build Runner"
  url = "https://git.xyser.com/"
  token = "3dc54666cacafd************e"
  executor = "docker"
  [runners.docker]
    tls_verify = false
    image = "alpine:latest"
    privileged = false
    disable_cache = false
    volumes = ["/cache"]
    shm_size = 0
    // 加入这行
    pull_policy = "if-not-present"
  [runners.cache]