image_types_wic.bbclass: capture verbose wic output by default

image_types_wic.bbclass: capture verbose wic output by default

Call wic with --debug to capture logs from wic internals
so that it's clear which partitions get created and which
files get copied where. wic plugins contain for example
race conditions which don't install files at all and thus
images fail to boot and it's not possible to debug these without
something in wic task logs.

As an example core-image-initramfs-boot do_image_wic
log is now 576 lines which is not excessive but very
important when debugging problems, especially race
conditions which are only hit in some builds in CI.

With all issues I have to deal within wic, I always
need to apply this change before I get to see any
details what wic and its plugins are doing. Thus I
strongly believe this verbose outuput should be the
default.

Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>