After the recent kernel changes, non linux-yocto builds stopped working
properly for two reasons:
a) ${S} was being reset to ${WORKDIR}/git for example and STAGING_KERNEL_DIR
did not contain the source
b) Most builds were using ${B} == ${S}
This patch adds a fixup to the unpack function to handle the case where
${S} != ${STAGING_KERNEL_DIR} and also set up the infrastrcture so that
B != S for kernel builds from now on. The kernel build system is one of the
best for supporting this and there is no good reason not to take advantage
of it.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
