chrono.cpp: suppress clock_gettime()

src/chrono.cpp

@@ -116,10 +116,16 @@ steady_clock::now()
 steady_clock::time_point
 steady_clock::now()
 {
+#ifdef __MINGW32__
+    timeval tv;
+    gettimeofday(&tv, 0);
+    return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
+#else
     struct timespec tp;
     if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
         __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
     return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
+#endif
 }
 #endif  // __APPLE__