This is deployed onto the containers on

• test-digitalocean-ubuntu1804_docker-x64-1
• test-digitalocean-ubuntu1804_docker-x64-2
• test-softlayer-ubuntu1804_docker-x64-1

I've not made any CI job changes yet.

there's some opportunities for some clever bash in here, but maybe keeping it simple-ish is good enough

Admittedly I didn't try but the docs for RUN (https://docs.docker.com/engine/reference/builder/#run) says Docker runs /bin/sh -c which I believe is dash (and not bash) on Ubuntu systems. We could use SHELL instead to specifically execute bash, but I think we'll end up with something less readable as that needs to be in JSON form.

are we going to add regular jobs for each of these? we're going to need to have a hard look at capacity I think

My initial thought was to add one job (well subjob of the linux-containered job) that would parse out the minimum ICU version from tools/icu/icu_versions.json and setup the "system" version of ICU to build based on that. The various versions of ICU in this PR is because each release line has a different minimum ICU -- I added the current minimum ICU for the release lines (12.x, 14.x, 16.x and master -- for 14.x we're planning on restoring the minimum ICU back to 65 but it's currently 67, nodejs/node#39068) plus ICU 69 (V8 9.2, nodejs/node#38990).

The other way we could do it is to test as many versions of ICU as possible (i.e. a new subjob for each ICU version and then VersionSelector.groovy to filter them by release line) but that will be more maintenance for the Build team (keeping VersionSelector.groovy updated, managing several icu* labels in Jenkins) and would be several new (sub)jobs which I would then share your concerns over capacity.