fortify: keep external files alive

This should eliminate sporadic failures, like the known double close in "seccomp".

Signed-off-by: Ophestra <cat@gensokyo.uk>

wl/conn.go

@@ -94,6 +94,7 @@ func bindRawConn(done chan struct{}, rc syscall.RawConn, p, appID, instanceID st
 
 			// keep socket alive until done is requested
 			<-done
+			runtime.KeepAlive(syncPipe[1].Fd())
 		}); err != nil {
 			setupDone <- err
 		}