Ensure that the kernel objtool utilities are processed by the library
bundler in order to ensure that they're usable on foreign systems with
different libc versions.

Fixes: a9f6fceb ("sdk: fix building external modules when CONFIG_STACK_VALIDATION=y")
Acked-by: Yousong Zhou <yszhou4tech@gmail.com>
Signed-off-by: Jo-Philipp Wich <jo@mein.io>