Enforce required cmake flags as explicit requirements

[jathu]

Summary

The build file currently turns on a bunch of implicitly dependent flags, perhaps unnecessarily. Let's make these dependencies explicit now.

For example, previously if EXECUTORCH_BUILD_EXTENSION_TRAINING was turned on, it would then turn on its own set of dependencies. This is good from a developer experience point of view because users would need to just turn on one flag. However, from a build point of view, it makes it harder to maintain and understand what flags are conflicting with one another. Now, if you want to build the training extension, you will have to explicitly turn on the required flags. However, with our build presets — most developers should not have to do to this!

I have created a follow up ticket to actually comb through the existing flags and trim the fat if necessary: #11458

Test plan

CI

cc @larryliu0820

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/11457

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❌ 2 New Failures, 1 Unrelated Failure

As of commit d189a21 with merge base 2bb567f ():

NEW FAILURES - The following jobs have failed:

• trunk / test-models-linux-aarch64 (emformer_join, portable, linux.arm64.2xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t 32d3c838a9d637a3c3f4e76bf9a8f1c6d84f545930a69346cefe29e32a400d9c /exec failed with exit code 1
• trunk / test-models-linux-aarch64 (linear, xnnpack-quantization-delegation, linux.arm64.2xlarge) / linux-job (gh)
  RuntimeError: Command docker exec -t 787316a292cc7e51caf9b59aaa4a5041957d42bbc08d58e1f65b289017e49061 /exec failed with exit code 1

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-models-linux (add_mul, portable, linux.2xlarge) / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

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