Allow CI workflow to access the secrets when run from the nightly_release workflow.

[arcra]

All our nightly release runs print the message Using read-only cache (no credentials) when it should be using the secret to use the cache build in this step of the workflow, even tho the secret is set.

The reason seems to be that this CI workflow is called from another workflow, and in such cases, the parent workflow must explicitly allow child workflows to access the secrets, as noted in the GitHub documentation here.