Using Swift from a Swift Package in an Objective C++ client

I am struggling with using Swift from a Swift package in an Objective C++ client. The autogenerated header does not seem to be visible in the client. For plain ObjectiveC, a standard @import ModuleName; works just fine.

One answer says that "SPM doesn't support generating the header", but it's clear from the build logs that the header is created -- I can see it on disk in a temporary build directory, alongside the modulemap. I just can't seem to figure out how to expose this header to the client.