https://bugs.gentoo.org/937500
https://github.com/machinezone/IXWebSocket/pull/538
Fix build with GCC 15.
--- a/third_party/msgpack11/msgpack11.hpp
+++ b/third_party/msgpack11/msgpack11.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstdint>
 #include <string>
 #include <vector>
 #include <map>