Automatic merge from submit-queue (batch tested with PRs 66190, 66871, 66617, 66293, 66891). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Unset CDPATH in build scripts

**What this PR does / why we need it**:
Currently trying to build k8s fails if you have CDPATH set in your env. This is a minor change that allows building k8s without manually unsetting the variable. 

```release-note
```