title: How to fail a job in Github Actions?
body: <p>I'm developing a Github actions workflow. This workflow runs on Linux, Mac, and Windows.</p>
  <p>As part of the workflow, I have to check whether 2 environment variables are equal. If they don't - fail the job.</p>
  <p>As described <a href="https://help.github.com/en/articles/contexts-and-expression-syntax-for-github-actions#about-context-and-expressions" rel="noreferrer">here</a>,  Github Actions support <code>if:</code> condition:</p>
  <pre><code>steps:
  - run: # How can I make a cross-platform failure here?
    if: ${{ envA }} != ${{ envB }}
  </code></pre>
  <p>How can I make the job fail if the above condition is true?
  In the beginning, I thought of a script, but there must be a more elegant way to fail a job.</p>