file names: /build /el_capitan /optional /recommended /yosemite etc All the files are created at the day I opened my mac for the first time (iMac (Retina 5K, 27-inch, Late 2015))
They look like zero byte files created by an error of some sort. A good culprit is a script that has a path variable that usually points somewhere else and doesn't catch that the parameter or variable is blank - so your home folder (the current working) directory gets spammed.
I'd be slightly concerned since it's creating these wrong - what else is going wrong in that script? Deleting wrong files, or worse?
I'd be interested to see what the detailed information is for them. You can get this information using Finder list view, or via Terminal with
ls -la. Whilst you're in Terminal, you could also do
file "/mavericks" and see what that comes back with - it identifies the file type by its contents.
Did you buy your Mac brand new or previously used?
Check the root directory on your hard drive (Go > Computer) to see if you have any more files like that floating around.
If those are the only ones, just delete them. They aren't doing anything and appear to be flotsam from the installation process. If your hard drive is littered with similar files, then reinstall the OS from scratch.