Thanks. For posterity the manifest is at https://download.swift.org/prebuilts/swift-syntax/601.0.1/swiftlang-6.2.0.9.909-manifest.json, which is the full version output from swift --version.
I just need this in case I need to manually download the artifacts to prime our corporate proxy.
Yes, it's derived from the Swift compilerVersion in swiftc -print-target-info.
Gave this a go using xcodebuild, but the build fails when "Build for Testing" (regular build works), both in xcode and our CI.
We are using a macro target in our Package.swift. This target is used by a Macros package that is then imported by other modules. Legacy previews is off, as mentioned in other comments.
cannot load module 'SwiftSyntax' built with SDK 'macosx15.5' when using SDK 'iphonesimulator18.5' appears for the macro target.
That's a known issue with this first release of the prebuilts.