package/kbd: Fix broken Makefile when host-gettext was built before kbd

This patch uses the same solution used for util-linux:
https://git.busybox.net/buildroot/commit/package/util-linux?id=71f279f9a2bd3f086f3d31fa5a669d3f638bee99

To trigger the bug just build host-gettext before kbd.

Fixes
http://autobuild.buildroot.net/results/87e/87ea83ae4e7b7640651acd5031a624ca42e5b348/
http://autobuild.buildroot.net/results/532/532684b98e050cf5b4c50786bc9e8825eab21f97/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>