wic: Honor APPEND
APPEND is used to add additional parameters to kernel by features, such
as read-only-rootfs. So we should honor this variable when we compose
the kernel parameter in wic. I know we also can resolve this kind of
issue by using the .wks.in template introduced by commit
42e870c5ed4b
("image_types.bbclass: support template .wks.in files for wic"), but the
APPEND is needed by all the wks, it would seems pretty ridiculous to me
to change all the .wks to .wks.in and then foist the APPEND into them.
So the APPEND is definitely deserved to export to the wic directly.
[Yocto #12809]
Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
