Add custom target for testprogs
Add custom target for testprogs

When we do `sudo make runtime-tests`, we'd like all the dependencies
to implicitly build. It makes it easier for CI to "just work".

That being said, you probably wanna avoid doing building the deps as
root because it'll mess up non-root builds.

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace