Add macos platform suppport to onnxruntime-extensions-c pod

[YUNQIUGUO]

As title.

• Currently it consumes a pre-release version of onnxruntime-objc pod (as the required new macos support is not yet released.)
• Validated in a macOS app with updated onnxruntime-extensions-c pod
• Pipeline changes for extensions.ios_packaging, successful build: https://aiinfra.visualstudio.com/Lotus/_build/results?buildId=390131&view=results

Motivation:

In order to allow macos support in SPM with one single Package.swift, extensions pod should include macos library support as the best solution though it has not been asked yet.

Note: validated with the dev pod archive as binary target for SPM (with platform macOS and iOS), it works as expected.