Fix missing null termination of a string in Getaddrinfo() in websocket_to_posix_proxy utility. (emscripten-core#25829)

`strncpy()` is evil that if the string length exceeds the copy length,
the destination string is left null-terminated. So null terminate
manually.

Author: juj

tools/websocket_to_posix_proxy/src/websocket_to_posix_proxy.c

@@ -1494,6 +1494,7 @@ void Getaddrinfo(int client_fd, uint8_t *data, uint64_t numBytes) {
   r->ret = ret;
   r->errno_ = errorCode;
   strncpy(r->ai_canonname, ai_canonname, MAX_NODE_LEN-1);
+  r->ai_canonname[MAX_NODE_LEN-1] = 0; // Null terminate output string if it truncated.
   r->addrCount = addrCount;
 
   struct addrinfo *ai = res;