- use LFS64 file/stat APIs only on glibc/Windows (absent in musl)
- use plain sched_priority outside glibc
- do not declare pow10(double) where the system provides C23 pow10() (musl)
- ICU is off by default: modern ICU (>= 75) needs C++17 for its headers,
the project is built with C++11; enable explicitly with -DICU=ON
- fix latent crash: PIThread::setThreadName() read the thread handle from
inside the new thread; the handle is not guaranteed to be visible before
start (musl publishes it later), rename the calling thread via
pthread_self() instead