mingw: fix 'struct tm' compilation issue

src/util-time.c

@@ -420,8 +420,10 @@ time_t SCMkTimeUtc (struct tm *tp)
     result += tp->tm_min;
     result *= 60;
     result += tp->tm_sec;
+#ifndef OS_WIN32
     if (tp->tm_gmtoff)
         result -= tp->tm_gmtoff;
+#endif
     return result;
 }
 
@@ -453,8 +455,10 @@ int SCStringPatternToTime (char *string, const char **patterns, int num_patterns
         tp->tm_hour = tp->tm_min = tp->tm_sec = 0;
         tp->tm_year = tp->tm_mon = tp->tm_mday = tp->tm_wday = INT_MIN;
         tp->tm_isdst = -1;
+#ifndef OS_WIN32
         tp->tm_gmtoff = 0;
         tp->tm_zone = NULL;
+#endif
         result = strptime(string, patterns[i], tp);
 
         if (result && *result == '\0')