generate_truth named a narrowed model's directory after the target
as typed, so three aliases of one target wrote three copies, and
the pipeline rebuilt the slug by hand to diff it. One function now
names the directory from the canonical target for both.
A target was canonicalised once for the run and kept as typed under
--all when platforms file it differently, so the --all build and a
--platform check named the same Batocera pack two ways. Each pack,
group, manifest and expected name now takes the target as its own
platform files it.
Abdessamad Derraz