configure: enable -Wunused-but-set-variable

configure.ac

@@ -726,6 +726,7 @@ AX_CHECK_COMPILE_FLAG([-Wlogical-op], [CFLAGS="$CFLAGS -Wlogical-op"],,[-Werror]
 AX_CHECK_COMPILE_FLAG([-Wmissing-include-dirs], [CFLAGS="$CFLAGS -Wmissing-include-dirs"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wold-style-definition], [CFLAGS="$CFLAGS -Wold-style-definition"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Winit-self], [CFLAGS="$CFLAGS -Winit-self"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Wunused-but-set-variable], [CFLAGS="$CFLAGS -Wunused-but-set-variable"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wfloat-equal], [CFLAGS="$CFLAGS -Wfloat-equal"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wsuggest-attribute=noreturn], [CFLAGS="$CFLAGS -Wsuggest-attribute=noreturn"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Werror=return-type], [CFLAGS="$CFLAGS -Werror=return-type"],,[-Werror])

src/lxc/commands.c

@@ -1198,7 +1198,6 @@ static int lxc_cmd_seccomp_notify_add_listener_callback(int fd,
 #ifdef HAVE_SECCOMP_NOTIFY
 	int ret;
 	__do_close_prot_errno int recv_fd = -EBADF;
-	int notify_fd = -EBADF;
 
 	ret = lxc_abstract_unix_recv_fds(fd, &recv_fd, 1, NULL, 0);
 	if (ret <= 0) {
@@ -1219,7 +1218,7 @@ static int lxc_cmd_seccomp_notify_add_listener_callback(int fd,
 		rsp.ret = -errno;
 		goto out;
 	}
-	notify_fd = move_fd(recv_fd);
+	move_fd(recv_fd);
 
 out:
 #else