image_types_wic: Move wic working directory

By default the wic working directory is placed under the output
directory. When invoking wic under bitbake, the wic output directory is
added to PSEUDO_PATHS_IGNORE to avoid issues with files being removed
from outside a pseudo environment (see oe-core commit ad8f5532).

However, wic will copy the rootfs directory into its working directory
if it needs to add or remove content before creating a filesystem image.
This copy of the rootfs directory must be tracked by pseudo in order to
keep the permissions correct in the resulting image. So we can't have
the wic working directory under a path in PSEUDO_PATHS_IGNORE unless
we like broken permissions.

To fix this the new '-w' argument to wic is used to move the working
directory away from the output directory.

Note that wic deletes the temporary working directory automatically
when it finishes creating an image so users won't normally see the
'tmp-wic' directory under WORKDIR.

Fixes [Yocto #14129]

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 4d071694)
Signed-off-by: Steve Sakoman <steve@sakoman.com>