It is strongly recommended that you install your development builds into a separate non-system location
This provides for a number of advantages:
- Your system installed version of KDE is untouched, meaning your normal desktop and applications remain stable and usable even if your development build breaks
- You can build and run multiple development versions of KDE at the same time, i.e. a stable branch for bug fixes and an unstable branch for new features
That said, the instructions provided are completely generic and will work for building a system install if you configure your environment to do so.