Updated instructions to create an ingress controller build

[lihan]

No description provided.

[k8s-ci-robot]

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[k8s-reviewable]

This change is 

[lihan]

signed

[coveralls]

Coverage remained the same at 45.509% when pulling 7b618cb on lihan:584-build-doc-update into c36d6ff on kubernetes:master.

[lihan]

I signed it!

[coveralls]

Coverage increased (+0.7%) to 46.17% when pulling 7b618cb on lihan:584-build-doc-update into c36d6ff on kubernetes:master.

[lihan]

I signed it!

[thelinuxfoundation]

bump the CLA check

[aledbf]

/lgtm

[aledbf]

@lihan thanks!