Sample Failures on macos - multidevice and callbackcpp

[bashbaug]

The multidevice and callbackcpp tests are failing on macos.

Specifically:

• multidevice (and multidevicecpp) is failing due to an error returned by clCreateSubBuffer, see: https://github.com/bashbaug/OpenCL-SDK/actions/runs/17273274320/job/49023554409
• callbackcpp is segfaulting for release builds only, see: https://github.com/bashbaug/OpenCL-SDK/actions/runs/17270551550/job/49013861064

We should debug these failures to check if they are PoCL issues or sample issues, and re-enable the tests when they are passing.