Introduce CMake workflow

[larryliu0820]

Stack from ghstack (oldest at bottom):

• -> Introduce CMake workflow #15804

CMake workflow combines configure and build into 1 command. Instead of
doing:

cmake --preset llm \
      -DEXECUTORCH_BUILD_CUDA=ON \
      -DCMAKE_INSTALL_PREFIX=cmake-out \
      -DCMAKE_BUILD_TYPE=Release \
      -Bcmake-out -S.
cmake --build cmake-out -j$(nproc) --target install --config Release

We can simply do cmake --workflow llm-release-cuda. This largely
reduces the burden of running these cmake commands.

Next step I'm going to create workflow for the popular runners (llama,
whisper, voxtral etc) and further simplify the build command

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15804

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 1 New Failure, 8 Pending, 6 Unrelated Failures

As of commit 8dd6a3c with merge base 6de1f4e ():

NEW FAILURE - The following job has failed:

• trunk / test-arm-cortex-m-size-test (zephyr-preset) / linux-job (gh)
  RuntimeError: Command docker exec -t de253eadb3c46fd30d1f02814af574391c3f61bdc43e14c91d899befd5fe8cbb /exec failed with exit code 1

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (detected as infra flaky with no log or failing log classifier)
• pull / unittest-editable / linux / linux-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• trunk / unittest-release / linux / linux-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe
• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_int8_static_quant_recipe

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[lucylq]

We can add some instruction on how to add a new worfklow. Is this correct?

To add a new workflow:
1. Add a configure preset, e.g. new-workflow
2. Add a build preset that depends on (1), e.g. new-workflow-install
3. You should be able to run cmake --workflow new-workflow-install

[larryliu0820]

Yeah. Let me add your words into README.md

[lucylq]

This is a great change, thank you!