[C++][FlightRPC] CI failing on macOS builds: reference to 'bp::child' is ambiguous

[felipecrv]

Describe the bug, including details regarding any error messages, version, and platform.

/Users/runner/work/arrow/arrow/cpp/src/arrow/flight/test_util.cc:113:32:
error: reference to 'child' is ambiguous
          std::make_shared<bp::child>(bp::search_path(executable_name_, search_path),

Component(s)

C++, FlightRPC

[raulcd]

isn't this related to #43746?

[felipecrv]

@raulcd yes. I suspected this had been caused by my recent work around the flight code, but it's indeed just a build config issue.