[static] Add busybox-static subpackage

NOTE: Currently the config doesn't match with dynamic. This should
be fixed in the future so that both busybox versions would have
same features.

Signed-off-by: Marko Saukko <marko.saukko@jollamobile.com>
Merge pull request #3 from saukko/master

[static] Add busybox-static subpackage