Use cpp subdirectory for RMM.

[bdice]

Description

Updates for rapidsai/rmm#1883.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The cmake-format.json is up to date with these changes.
• I have added new files under rapids-cmake/
  • I have added include guards (include_guard(GLOBAL))
  • I have added the associated docs/ rst file and update the api.rst

[robertmaynard]

We need to make this conditional based on the version returned from the json information.

We can have something like SPARK using latest rapids-cmake but pinned to a rmm/cudf before the cpp directory existed.

[bdice]

@robertmaynard Do you mean we need to check this across releases, or within the 25.06 release? Do users expect it is allowed to mix rapids-cmake 25.06 with RMM 25.04?

[robertmaynard]

Do users expect it is allowed to mix rapids-cmake 25.06 with RMM 25.04?

Yes. If we want to drop support for pre src directory versions of rmm we can add a deprecatation notice in 25.06 and remove in 25.08 or 25.10

[KyleFromNVIDIA]

The cpm_generate_pins-format-patches and cpm_generate_pins-override failures are due to @bdice's fork of RMM not having the v22.02.00 tag. Those errors will go away once we go back to using mainline RMM (or if @bdice adds that tag to his fork). Still looking at the other failures.

[KyleFromNVIDIA]

Looks like my commit fixed all the remaining test failures. CI is effectively clean now.

Addressed

[KyleFromNVIDIA]

/merge