Since when does Gitlab(-CI) Provide a Compiler or OS Framework? Gitlab-CI allows you to execute commands in some form of defined environment (Container based, insite a VM or on bare-metal), They have to make sure the commands are executed in the order you defined, and the output is then shown in the WebUI. Everthing run is "random" cli-tool you "found" somewhere.
If they aren't running Windows, I really doubt their skillset to give any kind of meaningful support.