From the "Killed", it looks like you're running out of memory and the OS has started killing off processes to keep things afloat. The set of measurements at the bottom of your transcript shows only 33% memory use, but I wonder if I could get a second opinion: what does "vmstat -S m -a" say on the VM before and after a failed "make"?
> I cannot find any piece of code in the VM
Take a look in /home/vagrant/dxr. Is there code in there? I think you will find that there is, as that's where peep.py lives, mounted with the rest of the code as part of a Virtualbox shared folder.
How much RAM does the host machine have? We have one other contrib with problems running DXR on a very small host.
You could try increasing RAM on the VM. I don't see why it should work in CI for us with the stock settings but fail for you, but it's worth a try.
Thanks for taking the time to ask for help. We'll get it figured out. :-)
Cheers,
Erik