CMP0157 is breaking the Windows nightlies

[compnerd]

https://ci-external.swift.org/job/swift-6.1-windows-toolchain/157/consoleText

This is caused by the lack of the early swift-driver on Windows. We need to disable CMP0157.

CC: @etcwilde @shahmishal

[Steelskin]

I believe this needs a CP of swiftlang/swift-corelibs-foundation#5180 into the release/6.1 branch. I'll get to it.

[Steelskin]

This seems to be fixed but the 6.1 toolchain build is failing on something else.