Add version check for node.js installation

[JappeHallunken]

I'm currently implementing https://github.com/louislam/uptime-kuma (I don't know if Stephan already asked you about it, I just started doing it) which depends on node.js.
For testing I did a lot of installing and reinstalling and every time I did this node.js was pulled and installed again, despite the fact that the current version is already present. So I added just some lines to do quick check to prevent this behaviour.

New behaviour:
If the currently installed version matches the newest node.js version the installation process is skipped.

[MichaIng]

I am not 100% sure whether we should add this. For testing, of course the re-download of Node.js each iteration is unnecessary, but end users won't do it that often, so that the chance for a new Node.js release isn't low either. And the way it is now, a reinstall also repairs Node.js, if anything about the instance is broken, though node -v at least guarantees that node itself works to a certain degree.

In any case, the installer has a version-listing as well, which could be used:

./node-install.sh -l

This lists official as well as unofficial builds, which are currently needed for ARMv6 and RISC-V: https://unofficial-builds.nodejs.org/download/release/index.tab

And both would require a logic to obtain or filter the versions by official/unofficial builds based on arch. This would be actually easier to implement at the installer itself (which I maintain anyway): https://github.com/MichaIng/nodejs-linux-installer
Adding a node -v check to skip download&install if it equals the obtained latest version from official or unofficial builds based on input, is even less additional code than here. I could add a -f/--force or -r/--repair option for those who need it.

[JappeHallunken]

Agreed.
Not sure if a version check or a force/repair option is really necessary. Since it's rarely reinstalled in practice, adding those options might be more annoying than helpful during frequent testing. I think it’s fine as it is then.