onnxruntime

Use xcode parallel build flags to speed up iOS CI that is timing out (#19570)

### Description
<!-- Describe your changes. -->
Provide specific xcodebuild flags instead of depending on cmake to do
the right thing.

This built in just over an hour with a ccache miss. Previous CIs with a
ccache miss were timing out after 150 minutes.


### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->