Feature: Fail all parallel steps if 1 of them fails

[raynix]

Given

steps:
  - label: "step 1.a"
    command:
      - ./1.a.sh

  - label: "step 1.b"
    command:
      - ./1.b.sh

  - wait
  - label: "step 2"

If step 1.a fails I would like step 1.b to fail or to be cancelled immediately as it's a waste of time for a buildkite agent to complete 1.b in such scenario.