Needs:parallel:matrix specifies a subset of the rows

What does this MR do and why?

Addressing the case 1 from the parent issue. See issue for details.
Case 2 is currently under discussion, so depending on the outcome of it, I will address it in the followup mr.

How to set up and validate locally

1. Checkout this branch and restart your server.
2. Paste below jobs into your .gitlab-ci.yml file

linux:build:
  stage: build
  script: echo "Building linux"
  parallel:
    matrix:
      - VAR1: 
         - aws
         - naws 
        VAR2:
          - monitoring
          - app1
          - app2
        VAR3:
          - aaa
          - bbb
        VAR4: 
          - sss
      - VAR1: 
          - gcp


  linux:rspec:
  script: echo inux:rspec
  stage: test
  needs:
    - job: linux:build
      parallel:
        matrix:
          - VAR1: [aws]

Pipeline should create 14 jobs. You can try adding VAR4,VAR5(and more) to linux:build and it will still work creating more jobs.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.