Function cbm_gmtime_r

src/foundation/compat.h:99–101

/* ── gmtime_r (Windows lacks it) ─────────────────────────────── */
#ifdef _WIN32
static inline struct tm *cbm_gmtime_r(const time_t *timep, struct tm *result) {
    return gmtime_s(result, timep) == 0 ? result : NULL;
}
#else
#define cbm_gmtime_r gmtime_r
#endif