kernel-devsrc: fix on-target module build for v5.8+
The kernel build is now more sensitive to changing build inputs,
like the compiler, linker, source tree location, versions, file
timestamps, etc.
When a difference is detected, the kernel build invokes a syncconfig
to update/regenerate files as required. That process may prompt, and
hence breaks automated tested and other workflows.
By default, we don't want this to happen so we make sure that auto*
timestamps are newer or equal to the .config timestap, we ensure that
autoconf.h is in the filesystem and that we've substituted the
cross tools used to build the kernel with the names that will be
on the target.
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
