Added core-image-minimal -> syslinux dependency to ensure
syslinux artifacts are available from core-image-minimal
build. This should fix test_iso_image, test_bootloader_config and
test_default_output_dir test cases.
Used --native-sysroot in test_image_vars_dir_long and
test_image_vars_dir_short test cases to point out to wic-tools
native sysrtoot.
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
