Process script directory for all configs

Even when only building kmods process the scripts directory. This
way the common.sh script will be generated and the zfs.sh script
can be used to load/unload the in-tree kernel modules.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #14027
Closes #14051