Use getthrid() on OpenBSD for fallback thread global thread

 id

Author: seanm

loguru.cpp

@@ -1104,6 +1104,8 @@ namespace loguru
 			#elif defined(__FreeBSD__)
 				long thread_id;
 				(void)thr_self(&thread_id);
+			#elif defined(__OpenBSD__)
+				pid_t thread_id = getthrid();
 			#elif LOGURU_PTHREADS
 				uint64_t thread_id = reinterpret_cast<uint64_t>(pthread_self());
 			#else