可以在HerokuCI上缓存Selenium和Chromebuildpack安装吗？

我刚开始使用HerokuCI.我有几个Selenium测试,所以我已经添加了buildpacks app.json.

{
  "buildpacks": [
    { "url": "heroku/ruby" }
  ],
  "environments": {
    "test": {
      "addons": ["heroku-postgresql:in-dyno", "heroku-redis:in-dyno"],
      "buildpacks": [
        { "url": "heroku/ruby" },
        { "url": "https://github.com/notvad/heroku-buildpack-selenium" },
        { "url": "https://github.com/heroku/heroku-buildpack-chromedriver" },
        { "url": "https://github.com/heroku/heroku-buildpack-google-chrome" }
      ],
      "env": {
        "REDIS_PROVIDER": "REDIS_URL",
        "RAILS_ENV": "test",
        "RACK_ENV": "test",
        "MALLOC_ARENA_MAX": 2,
        "LANG": "en_US.UTF-8",
        "TEST_API": 1
      },
      "scripts": {
        "test-setup": "./bin/setup-cc-test-reporter",
        "test": "./bin/test-with-cc-test-reporter"
      }
    }
  }
}

这些不断重建以及所有依赖项.

-----> Selenium app detected
bash: /tmp/buildpacks/b5ae60a477f2ba582d00a4ba23348059d40dea69cea6d982947f7c6afa72d2b8d69252449d43cbcf97a23341fd57300a3fef3224ace95482e1c0deaf8a844e4d/export: No such file or directory
bash: /tmp/buildpacks/b7af5642714be4eddaa5f35e2b4c36176b839b4abcd9bfe57ee71c358d71152b4fd2cf925c5b6e6816adee359c4f0f966b663a7f8649b0729509d510091abc07/export: No such file or directory
-----> Updating apt caches
       Hit:1 http://apt.postgresql.org/pub/repos/apt bionic-pgdg InRelease
       Hit:2 http://archive.ubuntu.com/ubuntu bionic InRelease
       Hit:3 http://archive.ubuntu.com/ubuntu bionic-security InRelease
       Hit:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
       Reading package lists...
-----> Fetching .debs for xserver-xorg-core libgl1-mesa-dri xvfb libglide3 xfs unzip
       Reading package lists...
       Building dependency tree...
       Package xfs is not available, but is referred to by another package.
       This may mean that the package is missing, has been obsoleted, or
       is only available from another source

E: Package 'xfs' has no installation candidate
-----> Installing adwaita-icon-theme_3.28.0-1ubuntu1_all.deb
-----> Installing at-spi2-core_2.28.0-1_amd64.deb

...and so on...

-----> Downloading and installing Selenium
-----> Writing profile script
-----> chromedriver app detected
bash: /tmp/buildpacks/b5ae60a477f2ba582d00a4ba23348059d40dea69cea6d982947f7c6afa72d2b8d69252449d43cbcf97a23341fd57300a3fef3224ace95482e1c0deaf8a844e4d/export: No such file or directory
bash: /tmp/buildpacks/b7af5642714be4eddaa5f35e2b4c36176b839b4abcd9bfe57ee71c358d71152b4fd2cf925c5b6e6816adee359c4f0f966b663a7f8649b0729509d510091abc07/export: No such file or directory
bash: /tmp/buildpacks/f55d0db8af2b8c70f2c0e028ef5430955852d9e4f07a06e333e54eb5264a81b9d1e77d1cc02851b4c7da30f6da47b13959e18a24c630212b899920d05f32a566/export: No such file or directory
-----> Looking up latest chromedriver version...
-----> Downloading chromedriver v2.43...
Archive:  /tmp/chromedriver.zip
  inflating: /app/.chromedriver/bin/chromedriver  
-----> Creating chromedriver export scripts...
-----> Google Chrome app detected
bash: /tmp/buildpacks/b5ae60a477f2ba582d00a4ba23348059d40dea69cea6d982947f7c6afa72d2b8d69252449d43cbcf97a23341fd57300a3fef3224ace95482e1c0deaf8a844e4d/export: No such file or directory
bash: /tmp/buildpacks/b7af5642714be4eddaa5f35e2b4c36176b839b4abcd9bfe57ee71c358d71152b4fd2cf925c5b6e6816adee359c4f0f966b663a7f8649b0729509d510091abc07/export: No such file or directory
bash: /tmp/buildpacks/f55d0db8af2b8c70f2c0e028ef5430955852d9e4f07a06e333e54eb5264a81b9d1e77d1cc02851b4c7da30f6da47b13959e18a24c630212b899920d05f32a566/export: No such file or directory
bash: /tmp/buildpacks/27353aa3b5edb2f8361186206e863f5d481f02805d02f0efdec439f3d30349a4fbdad2951af33a0492023fb0d90d26dafda6fe76f1b2d34f68564a98545f7022/export: No such file or directory
-----> Installing Google Chrome from the stable channel.
-----> Updating apt caches
       Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease
       Hit:2 http://apt.postgresql.org/pub/repos/apt bionic-pgdg InRelease
       Hit:3 http://archive.ubuntu.com/ubuntu bionic-security InRelease
       Hit:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
       Reading package lists...
-----> Fetching .debs for gconf-service

...and so on...

这占用了大部分测试运行时间.

这些安装可以缓存吗？