Update on "Add CMake preset for LLM"

Summary: By default turn on custom ops, optimized kernels, xnnpack. For
macOS/iOS turn on coreml and MPS.

Test Plan: Rely on CI jobs.

[ghstack-poisoned]

Author: larryliu0820

.github/workflows/build-presets.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        preset: [macos-arm64, pybind]
+        preset: [macos-arm64, pybind, llm]
     with:
       job-name: build
       ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}