Optional Multi-target Suport (Develop)

[jsfillman]

Changes:

• Uses latest upstream workflows (docker/build-push-action etc.)
• Can now optionally define extra build envs using the with platforms option:

jobs:
  build-develop-open:
    if: github.base_ref == 'develop' && github.event.pull_request.merged == false
    uses: kbase/.github/.github/workflows/reusable_build.yml@multi-target
    with:
      platforms: "linux/amd64,linux/arm64/v8,linux/s390x"
    secrets: inherit

Note: Defaults to linux/amd64 if above is missing, for backwards compatibility.

Discussion:

• Updated reusable workflows to use this input
• Tested via above job mod on multi-target branch
• Note the above actually fails in my test since the 390x version of Alpine (testing on db_zip2cloud repo) lacks some of the needed packages
• On variable setup:
  • I tried every way I could find to define once in the calling workflow, but it doesn't seem to pass to all the separate jobs
  • Also note, a matrix build would be cleaner, but it'd be much cludgier to modify
  • Current setup is an ok compromise, as a simple find & replace of the platform string is all that's needed

[jsfillman]

Pinging @ialarmedalien & @eapearson for thoughts. See notes in DEVOPS-1827

[ialarmedalien]

This seems like a reasonable compromise. Weird that there is no technical support for having an array of values for platforms!