Fix libFuzzer not building with pthreads on Windows (llvm#109525)

Fixes llvm#106871

(cherry picked from commit b4130be)

Author: Zentrik

compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp

@@ -239,6 +239,10 @@ size_t PageSize() {
 }
 
 void SetThreadName(std::thread &thread, const std::string &name) {
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD) ||                                 \
+    defined(_GLIBCXX_GCC_GTHR_POSIX_H)
+  (void)pthread_setname_np(thread.native_handle(), name.c_str());
+#else
   typedef HRESULT(WINAPI * proc)(HANDLE, PCWSTR);
   HMODULE kbase = GetModuleHandleA("KernelBase.dll");
   proc ThreadNameProc =
@@ -253,6 +257,7 @@ void SetThreadName(std::thread &thread, const std::string &name) {
       }
     }
   }
+#endif
 }
 
 } // namespace fuzzer