title: Gitlab-CI: set environment variables for both Linux and Windows
body: <p>I have a project that needs to be able to be built through a Gitlab-Runner on either Linux <em>or</em> Windows using the same <code>.gitlab-ci.yml</code> file in the Git repository. It's a simple build and I just want to use the <code>shell</code> executor.</p>
  
  <p>The problem is that the syntax for setting environment variables in <em>bash</em> (Linux) is different from <em>cmd</em> (Windows). One uses <code>export</code> the other <code>set</code>.</p>
  
  <p>How can I set up my environment without resorting to setting up a different <code>config.toml</code> on each runner? (Which also seems buggy on Linux when it comes to modifying <code>$PATH</code>, but that's another issue.)</p>