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.

[bashbaug]

Since the macos-13 runners are now retired, the Ruby testing is failing on macos also.

Do we want to fix this (we will still have coverage on Ubuntu), or disable the macos configs for now?