xtensa: enable multilib for dc233c and sample_controller

[dcpleung]

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This enables multilib support for building GCC. This is needed to support both CALL0 and Windowed ABIs.

Needs: https://github.com/zephyrproject-rtos/gcc/pull/23

[dcpleung]

~~If CI is building this correctly, we should be able to grab the artifacts in https://github.com/zephyrproject-rtos/sdk-ng/actions/runs/6043012028~~

CI actions won't produce correct binaries as it doesn't pull the GCC patch.

[nashif]

@dcpleung why is this still a fraft? Can you rebase?

[dcpleung]

This is needed for CALL0 API support, and also to aid in adding CALL0 support code. Since we still have no viable CALL0 code to test, there is not much point in merging it now. That's why it's in draft until we have something to test with.