lldb-vscode: Add a forgotten cast to void

"git push" works even with a dirty working tree. :/

Author: labath

lldb/tools/lldb-vscode/VSCode.cpp

@@ -47,6 +47,7 @@ VSCode::VSCode()
   int result = _setmode(fileno(stdout), _O_BINARY);
   assert(result);
   result = _setmode(fileno(stdin), _O_BINARY);
+  (void)result;
   assert(result);
 #endif
   if (log_file_path)