utils: build the dynamic experimental SDK

[compnerd]

Build the dynamic experimental SDK on Windows.

[compnerd]

@swift-ci please smoke test

[compnerd]

@swift-ci please test Windows platform

[aschwaighofer]

@compnerd

This looks like a likely culprit for https://ci-external.swift.org/job/swift-main-windows-toolchain-arm64/1446/ failing

2025-08-20T01:16:24.598Z]  (is the command line too long?)
[2025-08-20T01:16:24.598Z] <unknown>:0: warning: using (deprecated) legacy driver, Swift installation does not contain swift-driver at: 'C:\Users\swift-ci\jenkins\workspace\swift-main-windows-toolchain-arm64\build\1\bin\swift-driver-new.exe'

[2025-08-20T01:16:24.598Z] Error: Error: cmake.exe exited with code 1.
[2025-08-20T01:16:24.598Z] Invocation:
[2025-08-20T01:16:24.598Z]   C:\Program Files\CMake\bin\cmake.exe --build T:\x86_64-unknown-windows-msvc\ExperimentalDynamicFoundation --target install

[aschwaighofer]

Maybe also the cause of failure of the new failure of the windows build: https://ci-external.swift.org/job/swift-main-windows-toolchain/1536?