(Reported by Leah Neukirchen.)

If the bpf in /usr/lib64/dtrace is stripped, it is wrecked (we need the symbol table to figure out what to load), but we don't diagnose this: instead, we just emit a 'could not enable tracing' message.

It should be easy enough to validate that the bpf library has at least one known symbol in it and fail with a better error if not :)