Do not try to get node version unless node is installed

[luizkowalski]

I currently have Bun installed and just this morning, uninstalled Node. After that, I noticed that my Dockerfile keeps re-adding nodejs and npm. Debugging a little bit, the node_version method has a rescue that defaults to "lts" in case there's an error, and that's what happens when node command is not found. I figure that it should be safe to just not try to find a version if we are not using node anyways

[luizkowalski]

hmm, trying to run the failed test locally, but not only it fail with a different error, it also tries to add execjs to the Gemfile itself

gonna debug it tomorrow

[rubys]

execjs will need a runtime.... it now supports bun and the dockerfile generator could be enhanced to try to match the runtime you are otherwise using; but for now I presume that could be a separate pull request.