Avoid duplicate ops registration in macOS executor_runner (#19804)

### Summary

The macOS preset builds `executor_runner` with optimized kernels
enabled, so the top-level runner link logic already selects
`optimized_native_cpu_ops_lib` as the ops registration library.

`coremldelegate` was also linking `portable_ops_lib` and
`portable_kernels` through `EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER`.
Since `coremldelegate` is included through `executorch_backends`,
`executor_runner` could force-load both `portable_ops_lib` and
`optimized_native_cpu_ops_lib`. Their generated static initializers
register overlapping ATen kernels, causing `executor_runner` to abort
before `main()` with a duplicate registration error.

This removes the CoreML-side ops-lib link and removes the obsolete
`EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER` preset option. The CoreML
executor runner under `examples/apple/coreml/executor_runner` is not a
CMake target, so this option was not actually building that runner.

### Compatibility

The `coreml_executor_runner` built by
`examples/apple/coreml/scripts/build_executor_runner.sh` is unaffected.
That script builds the relevant CMake targets, then stages
`libportable_ops_lib.a` and `libportable_kernels.a` into
`examples/apple/coreml/executor_runner/libraries/`. The Xcode project
links those archives directly, independent of `libcoremldelegate.a`'s
internal link list, so the Xcode-built runner keeps working through its
own link line.

Other CMake consumers of `coremldelegate` already select an ops
registration library independently before force-loading
`coremldelegate`, so they are unaffected by removing the private
portable-kernel link from the delegate. Non-Apple platforms do not build
`coremldelegate` because `backends/apple/coreml/CMakeLists.txt` is gated
by `if(APPLE)`. The iOS and iOS-simulator presets never set the removed
option.

### Test plan

```bash
cmake --preset macos
cmake --build cmake-out --target executor_runner --config Debug -j
./cmake-out/Debug/executor_runner
cmake --build cmake-out --target coremldelegate --config Debug -j
```

Verified the `executor_runner` link line no longer contains
`libportable_ops_lib.a` or unprefixed `libportable_kernels.a`.
`liboptimized_native_cpu_ops_lib.a` is still force-loaded.
`liboptimized_portable_kernels.a` is still present, which is expected
because it is one of `optimized_native_cpu_ops_lib`'s kernel libraries.

Running without `--model_path` now reaches `main()`, resets the
threadpool, and fails only on the expected missing `model.pte` path
instead of aborting during static kernel registration.

Authored with Claude.

cc @larryliu0820 @GregoryComer @kimishpatel @YifanShenSZ @cymbalrush
@metascroy

Co-authored-by: Digant Desai <digantdesai@meta.com>

Author: devin-lai

backends/apple/coreml/CMakeLists.txt

@@ -230,12 +230,6 @@ if(APPLE)
 
   executorch_target_link_options_shared_lib(coremldelegate)
 
-  if(EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER)
-    target_link_libraries(
-      coremldelegate PRIVATE portable_ops_lib portable_kernels
-    )
-  endif()
-
   target_compile_options(
     coremldelegate PRIVATE -fobjc-arc -fno-exceptions -x objective-c++
                            -Wno-null-character -Wno-receiver-expr

tools/cmake/preset/default.cmake

@@ -194,10 +194,6 @@ define_overridable_option(
 define_overridable_option(
   EXECUTORCH_BUILD_VGF "Build the Arm VGF backend" BOOL OFF
 )
-define_overridable_option(
-  EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER "Build CoreML executor runner." BOOL
-  OFF
-)
 define_overridable_option(
   EXECUTORCH_BUILD_WASM "Build the ExecuTorch JavaScript API" BOOL OFF
 )

tools/cmake/preset/macos.cmake

@@ -9,4 +9,3 @@ include(${PROJECT_SOURCE_DIR}/tools/cmake/preset/apple_common.cmake)
 set_overridable_option(EXECUTORCH_BUILD_EXTENSION_EVALUE_UTIL ON)
 set_overridable_option(EXECUTORCH_BUILD_EXTENSION_RUNNER_UTIL ON)
 set_overridable_option(EXECUTORCH_BUILD_EXECUTOR_RUNNER ON)
-set_overridable_option(EXECUTORCH_COREML_BUILD_EXECUTOR_RUNNER ON)