allarch: Fix allarch corner case

allarch: Fix allarch corner case

Most of the allarch code is conditional and only set if the recipe remains marked
as allarch. The qemu wrapper handling is not handled in the same way however and
is unconditional.

Move the code to some slightly uglier inline python to allow it to be conditional
and match the way the rest of the code works.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit dfd704f1741dccd9a85338c5d45dee4be079064d)
Signed-off-by: Steve Sakoman <steve@sakoman.com>