Set umask 0022 when building

[thockin]

Some binaries now run as non-root (kube-scheduler). When umask is 0027,
for example, the container image we build has the binary 0750, which is
not executable by the non-root UID.

/kind bug

NONE

[dims]

/lgtm

[thockin]

/retest

[justaugustus]

@thockin -- do you know when this change happened i.e., how far should we cherry pick it back?

/hold given that this affects a release artifact, I think it should have a release note.
cc: @kubernetes/release-engineering
/area release-eng
/retest

[thockin]

I think it has ALWAYS been present, but didn't matter because things like scheduler were running as root. Now that it's not, suddenly umask matters. You can manually check previous artifacts for the mode of the executables. If you want to backport to all living branches that would be fine with me.

[thockin]

WRT release note - it shouldn't have any impact on artifacts (as far as I can guess, release-team must be using a safe umask already). If I looked at a k8s changelog and saw something about umask, I would be confused why I care.

[thockin]

@justaugustus can we merge this?

[justaugustus]

@thockin -- we sure can!
/lgtm
/approve
/hold cancel

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