Compatibility updates for gradle 9.x.x

[jclyne]

Changes to kotlin-sdk-core/build.gradle.kts to be compatible with gradle 9.x.x

Motivation and Context

If including this project into a composite build that uses gradle 9.x.x, recent changes to the build.gradle.kts are not compatible.

How Has This Been Tested?

The build still works with gradle 8.x

Breaking Changes

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[Copilot]

Pull Request Overview

This PR updates the Kotlin SDK build script to be compatible with Gradle 9.x.x by converting deprecated property assignment syntax to the newer .set() method syntax.

• Updated library property assignment to use .set() method
• Updated ignoreFileOverride property assignment to use .set() method

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[kpavlov]

Thank you, @jclyne