Fix build for 3DS.

Public issue https://github.com/mackron/miniaudio/issues/902

miniaudio.h

@@ -16149,7 +16149,7 @@ static ma_result ma_thread_create__posix(ma_thread* pThread, ma_thread_priority
     int result;
     pthread_attr_t* pAttr = NULL;
 
-#if !defined(__EMSCRIPTEN__)
+#if !defined(__EMSCRIPTEN__) && !defined(__3DS__)
     /* Try setting the thread priority. It's not critical if anything fails here. */
     pthread_attr_t attr;
     if (pthread_attr_init(&attr) == 0) {