I guess the version of the build tools doesn’t change, so it would be nice to check if they are already installed and grey the control out, if so.
It’s safer to leave that up to the build tools installer. Say we do an update later and somehow don’t check the proper registry keys / folder names / etc for the updated version (or the newer version the installer installs as it has some self-update behavior) we end up with an even worse situtation…