intel: build hddimg by default

The useful mkefi.sh script requires an hddimg image, so we should build
hddimg's by default for Intel builds.

While we're at it, drop live per Jan-Simon's recommendations, so that we
have just wic and hddimg.

Change-Id: I24bfc03e9f357f3b8784267cc4537e4ff07d236e
Signed-off-by: Martin Kelly <mkelly@xevo.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10565
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: 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>