qemux86-64: build vmdk.xz images

qemux86-64: build vmdk.xz images

Generate vmdk.xz images by default.

Change-Id: I9a7638cd9a24083603b3dee80be553bccaf375de
AGL-Issue: SPEC-513
Signed-off-by: Matt Porter <mporter@konsulko.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/9029
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>