Fix poll.h warning on musl

--- include/utils/socket.hpp.orig
+++ include/utils/socket.hpp
@@ -1,7 +1,7 @@
 #pragma once

 #include <fcntl.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <sys/socket.h>
 #include <sys/un.h>