Upgrade Docker Ruby image from stretch to buster fails with libicudata

[shleeable]

Worked fine out of the box with stretch.

LoadError: libicudata.so.57: cannot open shared object file: No such file or directory - /home/circleci/projects/mastodon/vendor/bundle/ruby/2.6.0/gems/charlock_holmes-0.7.7/lib/charlock_holmes/charlock_holmes.so

Charlock doesn't seem to like buster because libicudata 57 is not available in buster (63). https://packages.debian.org/buster/libicu-dev

I've tried and failed to resolve this.

[shleeable]

FYI: I'm trying to upgrade on this repo - https://github.com/tootsuite/mastodon/blob/master/.circleci/config.yml

[LeZuse]

We had the same problem, but now we are able to run just fine on ruby 2.7