Snowball: Build a device tree file if needed

The tracking build uses the linux-linaro-tracking kernel and needs
a device tree file to boot.

Should really check if a device tree file is needed. Instead checks
if there is a vendor tarball to figure out if this is the tracking
build.

Change-Id: I398e1abc070356e27e3b4cd200edfa69e4e3d8d7
1 file changed