micro optimization in log_msg constructor

include/spdlog/details/log_msg.h

@@ -16,17 +16,18 @@ namespace details {
 struct log_msg
 {
     log_msg() = default;
+
     log_msg(const std::string *loggers_name, level::level_enum lvl)
         : logger_name(loggers_name)
         , level(lvl)
-    {
 #ifndef SPDLOG_NO_DATETIME
-        time = os::now();
+        , time(os::now())
 #endif
 
 #ifndef SPDLOG_NO_THREAD_ID
-        thread_id = os::thread_id();
+        , thread_id(os::thread_id())
 #endif
+    {
     }
 
     log_msg(const log_msg &other) = delete;