[v6.d REVIEW] Improve .= new shaped array test
[v6.d REVIEW] Improve .= new shaped array test

Test we actually got right result.
(tested with .perl's rather than is-deeply, because the latter
dies with partially dim. views NYI)
Orig: https://github.com/perl6/roast/commit/1f05be281

dogbert17/roast,perl6/roast,dogbert17/roast