Fix RunBuildToolTaskTest assertions

[gayaldassanayake]

Purpose

With https://github.com/ballerina-platform/ballerina-lang/pull/42485, the RunBuildToolTaskTest needs to be updated to match the change to throw an error early without going to the compilation stage.

Approach

Describe how you are implementing the solutions along with the design details.

Samples

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Remarks

List any other known issues, related PRs, TODO items, or any other notes related to the PR.

Check List

• [ ] Read the Contributing Guide
• [ ] Updated Change Log
• [ ] Checked Tooling Support (#)
• [ ] Added necessary tests
  • [ ] Unit Tests
  • [ ] Spec Conformance Tests
  • [ ] Integration Tests
  • [ ] Ballerina By Example Tests
• [ ] Increased Test Coverage
• [ ] Added necessary documentation
  • [ ] API documentation
  • [ ] Module documentation in Module.md files
  • [ ] Ballerina By Examples