Make the test suite pass on Windows

[compnerd]

Description

Tracker for enabling the SPM self-hosted test suite on Windows.

Expected behavior

No response

Actual behavior

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Steps to reproduce

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Swift Package Manager version/commit hash

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Swift & OS version (output of swift --version ; uname -a)

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[compnerd]

swiftlang/swift#71341 introduces support to run the SPM test suite with self-hosted building. In the mean time, we have swiftlang/swift#71349 to use cross-repository testing before we can enable the self-hosted test suite in all builds (currently the tests fail).