xserver: Just dup fd instead of two fcntls to get a non-O_CLOEXEC fd

Yeah, it's the same number of lines of code, but this actually checks
the error return.

src/xserver-launcher.c

@@ -1296,7 +1296,7 @@ weston_xserver_handle_event(int listen_fd, uint32_t mask, void *data)
 {
 	struct weston_xserver *mxs = data;
 	char display[8], s[8];
-	int sv[2], flags;
+	int sv[2], client_fd;
 
 	if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sv) < 0) {
 		fprintf(stderr, "socketpair failed\n");
@@ -1308,11 +1308,11 @@ weston_xserver_handle_event(int listen_fd, uint32_t mask, void *data)
 	case 0:
 		/* SOCK_CLOEXEC closes both ends, so we need to unset
 		 * the flag on the client fd. */
-		flags = fcntl(sv[1], F_GETFD);
-		if (flags != -1)
-			fcntl(sv[1], F_SETFD, flags & ~FD_CLOEXEC);
+		client_fd = dup(sv[1]);
+		if (client_fd < 0)
+			return 1;
 
-		snprintf(s, sizeof s, "%d", sv[1]);
+		snprintf(s, sizeof s, "%d", client_fd);
 		setenv("WAYLAND_SOCKET", s, 1);
 
 		snprintf(display, sizeof display, ":%d", mxs->display);