Cannot generate gcov data with `create_gcov`

Hi,

I've been profiling QEMU and would like to use autofdo to generate a gcov file to test some PGO scenarios. I'm currently in Ubuntu Noble 24.04 with autofdo 0.19-3 installed, and after generating a sizeable profile (around 800 Mb) with the following command:

```
sudo perf record \
-e br_inst_retired.near_taken \
--branch-any \
-p "${qemupid}" \
--all-cpus \
-F 99 \
--output="${perfoutput}" \
--call-graph fp &
```

I'm now attempting to convert it to gcov by invoking:

```
sudo create_gcov -profiler perf -profile perf-hello-1.data -gcov perf-hello-1.gcov -gcov_version 2 -binary /usr/bin/qemu-system-riscv64 -use_lbr 0
```

What I get is the following:

```
E20240628 22:18:15.648012 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648159 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648185 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648203 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648221 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648238 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648255 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648276 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648315 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648331 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648344 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648360 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648375 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648392 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648408 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648427 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648443 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648459 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648473 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648485 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648496 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648509 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648521 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648538 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648556 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648572 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648589 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648607 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648624 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648641 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648658 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.648674 382826 perf_serializer.cc:234] Unknown event type: 18
E20240628 22:18:15.648692 382826 perf_serializer.cc:234] Unknown event type: 17
E20240628 22:18:15.649129 382826 perf_serializer.cc:247] Unknown event type: 82
E20240628 22:18:28.603147 382826 perf_parser.cc:248] Unknown event type: 17
```

After that, I see `perf-hello-1.gcov` with only 1.6Kb, and nothing useful in it. `dump_gcov` isn't helpful, as it doesn't display anything.

My QEMU binary isn't stripped and still contains all debug symbols.

Any tips on how to proceed here?

Thanks.