[CI] Disjoint pool CMake warning with Compatibility v0.11.0-dev1

[KFilipek]

There is unused CMake variable during Compatibility (v0.11.0-dev1) build:

 CMake Warning:
  Manually-specified variables were not used by the project:

    UMF_BUILD_LIBUMF_POOL_DISJOINT

Source: https://github.com/oneapi-src/unified-memory-framework/actions/runs/13497228765/job/37709365720

Environment Information

• UMF version (hash commit or a tag): Latest
• OS(es) version(s): Ubuntu
• kernel version(s): N/A
• compiler, libraries, and other related tools version(s): N/A

Please provide a reproduction of the bug:

Run any PR that will trigger Compatibility (v0.11.0-dev1) job.

How often bug is revealed:

Always

Actual behavior:

 CMake Warning:
  Manually-specified variables were not used by the project:

    UMF_BUILD_LIBUMF_POOL_DISJOINT

Expected behavior:

Details

Additional information about Priority and Help Requested:

Are you willing to submit a pull request with a proposed change? (Yes, No)

Requested priority: (Showstopper, High, Medium, Low)