net/SocketDescriptor: fix SOCK_NONBLOCK flag in CreateSocketPairNonBlock()

src/net/SocketDescriptor.cxx

@@ -192,14 +192,14 @@ SocketDescriptor::CreateSocketPairNonBlock(int domain, int type, int protocol,
 					   SocketDescriptor &a,
 					   SocketDescriptor &b) noexcept
 {
-#ifdef SOCK_CLOEXEC
-	/* implemented since Linux 2.6.27 */
-	type |= SOCK_CLOEXEC;
+#ifdef SOCK_NONBLOCK
+	type |= SOCK_NONBLOCK;
 #endif
+
 	if (!CreateSocketPair(domain, type, protocol, a, b))
 		return false;
 
-#ifndef __linux__
+#ifndef SOCK_NONBLOCK
 	a.SetNonBlocking();
 	b.SetNonBlocking();
 #endif