The decomp's src/sched.h (N64 OSSc* scheduler) is on the include path and
shadows the system header. libstdc++'s <thread>/<mutex> gthr headers in the
fast3d C++ TUs #include <sched.h> and need the real one (cpu_set_t,
sched_yield) -- with -std=gnu++20 libstdc++ defines _GNU_SOURCE so
<pthread.h> also references cpu_set_t. New shim: C++ -> generated
hostsched.h (absolute path, hoststring pattern); C -> #include_next so
src/sched.h still wins as before. Windows build verified green (240/241).
James Dansereau
fe7a34c56e