Update CMakeLists.txt

[compnerd]

Add missing reference to Utilities/SequenceExtensions.swift which was failed to be updated with #179

Replace this paragraph with a description of your changes and rationale. Provide links to an existing issue or external references/discussions, if appropriate.

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[natecook1000]

@swift-ci Please test