acpi-build: Partially revert dac1e93093f9306c114f410785c99aa5261539b4

It touched the acpi test by mistake, removed that hunk.

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
acpi-test: retain both asl and aml files on failure

Updated the error message while at it.

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
acpi-test: issue errors instead of warnings when possible

If the expected (offline) acpi tables loaded correctly,
it is safe to assume the iasl installation is OK and
issue an error if the actual tables failed to load.

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>