xtools: fix some build issues

$DTC wasn't exported, causing a build failure if it wasn't
defined outside the build system.

The provided ct-ng configuration files define
CT_TARGET_VENDOR="zephyr". Fix CROSS_COMPILE definition so
that the compiler can be found.

Change-Id: I4e25c775e1f02a435704b6a874adb221c677b13a
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
1 file changed