kernel.bbclass: Add cleandirs for do_shared_workdir
We add the kernel-build-artifacts to the cleandirs list to ensure
that there are no remaining artificats in the kernel-build-artifacts
directory which is STAGING_KERNEL_BUILDDIR. Without this change
multiple System.map files are visiable in the STAGING_KERNEL_BUILDDIR,
which could cause problems for some tools.
[YOCTO #11880]
Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
