try to avoid the error "conflicting declaration 'typedef DWORD

pthread_t'" etc.

src/windows/port.h

@@ -136,6 +136,7 @@ typedef int pid_t;
 #endif  // _MSC_VER
 
 // ----------------------------------- THREADS
+#ifndef __MINGW32__
 typedef DWORD pthread_t;
 typedef DWORD pthread_key_t;
 typedef LONG pthread_once_t;
@@ -147,6 +148,7 @@ inline struct tm* localtime_r(const time_t* timep, struct tm* result) {
   localtime_s(result, timep);
   return result;
 }
+#endif
 
 inline char* strerror_r(int errnum, char* buf, size_t buflen) {
   strerror_s(buf, buflen, errnum);