add flag to xcodebuild to skip package plugin validation (#57)

# Skip Package Plugin Validation

## ♻️ Current situation & Problem
Xcode projects relying on package plugins do not run successfully with
our Xcode build workflow.
To resolve this issue an additional build argument should be added to
skip the plugin validation.


## ⚙️ Release Notes 
- add build argument skipPackagePluginValidation to Xcode build command
in the Xcode build workflow


### Code of Conduct & Contributing Guidelines 

By submitting creating this pull request, you agree to follow our [Code
of
Conduct](https://github.com/StanfordBDHG/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordBDHG/.github/blob/main/CONTRIBUTING.md):
- [x] I agree to follow the [Code of
Conduct](https://github.com/StanfordBDHG/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordBDHG/.github/blob/main/CONTRIBUTING.md).

.github/workflows/xcodebuild-or-fastlane.yml

@@ -362,6 +362,7 @@ jobs:
             CODE_SIGNING_REQUIRED=NO \
             CODE_SIGN_IDENTITY="" \
             OTHER_SWIFT_FLAGS="\$(inherited) $ENABLE_TESTING_FLAG" \
+            -skipPackagePluginValidation \
           | xcpretty
     - name: Fastlane
       if: ${{ inputs.fastlanelane != '' }}