build: improve detection of eBPF support
build: improve detection of eBPF support

Summary:
```
Just checking for the `sys/sdt.h` header isn't enough, as systems like
macOS have the header, but it doesn't actually have the dtrace probes,
which leads to compile failures.
```

Backport of [[https://github.com/bitcoin/bitcoin/pull/22238 | core#22238]].

Test Plan:
  cmake -GNinja .. -DENABLE_TRACING=ON
  ninja

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D12636

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