Fix bitrot

[VorpalBlade]

Fixes #14 plus some other issues (such as not working with modern bpftrace).

This is only lightly tested (using Arch Linux), but recreating the demo from the video works. But I also managed to get it to error out with an invalid bpftrace program at one point (not sure what I did). However, this PR takes it from not working at all, to working a bit.

cc @NHOrus as you opened a bug about failing to build with cmake 4. Maybe you are interested in this? I suspect upstream is actually entirely dead. (But this is quite a neat tool, if someone wants to build on this, which I don't think will be me, I just wanted to experiment with it.)