Stop using HDDDIR in isoimage-isohybrid wic plugin.
This variable is set by hddimg code, which is going to be
removed soon.
All required artifacts should be available from ISODIR.
wic-image.bbclass has been modified to build iso artifacts,
so it should be safe to remove usage of HDDDIR.
[YOCTO #10835]
(From OE-Core rev: 4ceb0df10db7254b290784cabc5279ffa2b946a4)
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>