Only output CUDA architectures we are building for once

[robertmaynard]

Description

When multiple projects inside the root level all use rapids-cmake we would previously output the CUDA architectures which would all have the same values.

Checklist

• I am familiar with the Contributing Guidelines.
• The documentation is up to date with these changes.
• The cmake-format.json is up to date with these changes.

[robertmaynard]

/merge