Because this is in a subdirectory, it requires some extra `mkdir -p`
and some `nobase_` variables. Make all the installed-tests `nobase_`
for consistency.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=99825
Reviewed-by: Andre Moreira Magalhaes <andre.magalhaes@collabora.co.uk>
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
