[libc++][Windows] Enable thread::hardware_concurrency to support more than 64 processors

Author: YexuanXiao

libcxx/src/thread.cpp

@@ -74,9 +74,7 @@ unsigned thread::hardware_concurrency() noexcept {
     return 0;
   return static_cast<unsigned>(result);
 #elif defined(_LIBCPP_WIN32API)
-  SYSTEM_INFO info;
-  GetSystemInfo(&info);
-  return info.dwNumberOfProcessors;
+  return static_cast<unsigned>(GetActiveProcessorCount(ALL_PROCESSOR_GROUPS));
 #else // defined(CTL_HW) && defined(HW_NCPU)
   // TODO: grovel through /proc or check cpuid on x86 and similar
   // instructions on other architectures.