Arm backend: Add arm-baremetal CMake preset

[AdrianLundell]

• Executorch may be cross compiled for arm-baremetal targets using 'cmake --preset arm-baremetal'
• Adds a new flag EXECUTORCH_BUILD_ARM_ETDUMP used in the preset to easy enabling of ET_DUMP.
• backend/arm/scripts/build_executorch.sh is updated to use the new preset with same behaviour as before.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

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❌ 1 New Failure

As of commit 2880783 with merge base bedce91 ():

NEW FAILURE - The following job has failed:

• trunk / test-arm-cortex-m-size-test (bare_metal) / linux-job (gh)
  RuntimeError: Command docker exec -t f8deebe4f97e71e7195688d861db602875b8ceeb2ae7bbe978088e38043180eb /exec failed with exit code 1

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[digantdesai]

Though this PR is OK, I want to brainstorm here a bit more.

There are two, I think, orthogonal things we are mixing here, (1) Arm-ness, (2) Baremetal-ness. Can we split? For the preset its OK, I am talking about things like EXECUTORCH_BUILD_ARM_BAREMETAL the things it guards are not strictly related to Arm.

This will come up when we try to do Arm Cortex-m + Ethos on Zephyr. Passing ARM_BAREMETAL would be confusing at best.

[AdrianLundell]

Good point, changing it to something like EXECUTORCH_BUILD_ARM_ETHOSU seems reasonable to me.

[digantdesai]

I guess depends on the things we want to guard with this build flavor. We need to split this EXEUCTORCH_BUILD_ARM_BAREMETAL into EXECUTORCH_BUILD_ARM_ETHOSU and EXECUTORCH_BUILD_BAREMETAL. I can also see Cortex-M (no NPU) builds and not sure if the ETHOSU is the right suffix either.