Since we want to be able to stop unpacking to WORKDIR, correct the WORKDIR
references in recipe do_compile/do_install tasks to use UNPACKDIR in the
appropraite places instead.
(From OE-Core rev: d73595df69667fe9d12ecd407b77a0b8dae2109c)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>