buildroot

vde2: enable building host package

In preparation of enabling vde2 support in host-qemu package.

Signed-off-by: Simon Maes <simonn.maes@gmail.com>
[Thomas:
 - add HOST_VDE2_CONF_OPTS and HOST_VDE2_MAKE, like we have for the
   target variant.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>