Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here: https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md.

Add spiffxp to OWNERS files in bash-heavy dirs

I'm comfortable approving changes in hack/, I think I still need
to build up a corpus of reviews in build/ and cluster/ before I'm
comfortable asking for those rights. I'm willing to be voluntold
otherwise if existing approvers feel differently.

Approvers, WDYT?

```release-note
NONE
```