What swiftc options are sufficient to create a *.DEBUG.dylib file for previews

Xcode 16 has a new requirement for some build targets (eg. those using previews) to produce a .DEBUG.dylib file.

If you have an externally managed build process that invokes swiftc, what options are needed to produce such a file?

What swiftc options are sufficient to create a *.DEBUG.dylib file for previews
 
 
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