fixing cross-compile builds, relates #170

src/ua_types.c

@@ -267,11 +267,13 @@ UA_TYPE_AS(UA_DateTime, UA_Int64)
 #define HUNDRED_NANOSEC_PER_SEC (HUNDRED_NANOSEC_PER_USEC * 1000000LL)
 
 #ifdef __MINGW32__
+#ifndef timezone
 struct timezone {
   int tz_minuteswest;
   int tz_dsttime;
 };
 #endif
+#endif
 #ifdef _WIN32
 static const unsigned __int64 epoch = 116444736000000000;
 int gettimeofday(struct timeval *tp, struct timezone *tzp);