Also #include <sys/uio.h>.

diff --git a/dlls/winsock/socket.c b/dlls/winsock/socket.c
index a33ffbf..90262d6 100644
--- a/dlls/winsock/socket.c
+++ b/dlls/winsock/socket.c
@@ -54,6 +54,7 @@
 #ifdef HAVE_SYS_WAIT_H
 # include <sys/wait.h>
 #endif
+#include <sys/uio.h>
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif