Use crossplane/build submodule

[turkenf]

Description of your changes

See https://github.com/crossplane/crossplane/issues/1583 for context.

This PR changes upbound/build submodule to crossplane/build submodule.

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] ~Added backport release-x.y labels to auto-backport this PR if necessary.~

How has this code been tested

Pipelines are green and a successful uptest run: https://github.com/crossplane-contrib/provider-upjet-gcp/actions/runs/9302315455

[turkenf]

/test-examples="examples/cloudplatform/serviceaccount.yaml"

Wrong path

[turkenf]

/test-examples="examples/cloudplatform/v1beta1/serviceaccount.yaml"