CI: Print out variables sent to `build-ci` in `Setup CI` job

[CodeGat]

Thanks @harshula for bringing this up!

Background

It would be useful to see what constant variables are passed to the matrix job in the Setup CI job.

Add a ::notice:: that notes the value for *-ref variables (among others, if needed).

Workaround

• Currently, one can use an instance of the matrix job, going into the Set up job step, and reading the Inputs section in that step, to get those variables.