cxx/core/log: fix thread_pool on MacOS
Fixes the following issue on MacOS with latest llvm/libc++/libunwind:
[*** LOG ERROR #0001 ***] [2025-05-22 11:34:41] [CSCP] async log: thread pool doesn't exist anymore [../cxx/constellation/satellite/BaseSatellite.cpp(95)]
Probably some thread-local static issue