[CUB] Add relocatable test installation

[ratnachandugembali-lgtm]

Summary

Adds an optional relocatable installation for CUB runtime tests using RAPIDS CMake.

• registers CUB test executables with a cub-tests install component
• installs RAPIDS CTest resource metadata and GPU-aware test launch support
• packages CUB's run_test.cmake and compute-sanitizer suppressions
• preserves the existing small/large GPU resource claims in installed CTest registrations
• updates RAPIDS CMake to v26.08.00, which supports rewriting nested test-command arguments during relocation

Implementation

Each runtime registration uses INSTALL_COMPONENT_SET cub-tests. The executable is recorded with INSTALL_TARGET, allowing rapids_test_install_relocatable() to install the target and regenerate CTestTestfile.cmake with install-tree paths.

CUB-specific support files are staged under the build tree and installed with the same component because RAPIDS CMake cannot infer them:

• cub/test/run_test.cmake
• ci/compute-sanitizer-suppressions.xml

The component remains EXCLUDE_FROM_ALL, so normal CCCL installation does not include the test package.

Usage

cmake --install <cub-build-dir> \
  --prefix <install-prefix> \
  --component cub-tests

ctest \
  --test-dir <install-prefix>/bin/cub-tests \
  -j8 \
  --output-on-failure

The installed directory can be moved before running CTest. The destination system must still provide compatible CUDA runtime libraries and cmake/ctest on PATH.

Validation

• pre-commit run --files cmake/CCCLGetDependencies.cmake cmake/RAPIDS.cmake cub/test/CMakeLists.txt
• reviewed against the RAPIDS CMake v26.08.00 relocatable-test implementation and tests

A complete CUB configure, install, relocation, and runtime test has not yet been run in this local environment because nvcc is unavailable.

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