This (exact) issue happens to me too and I am currently working on fix (fixing my own project). I suspect this issue may be closely related to
and related bug report filed in jira. [SR-3169] lldb stops working when C module includes a header outside of module's include/ dir · Issue #4577 · apple/llvm-project · GitHub
This issue also could be related to SwiftPM and LLDB but unlike the first thread, I am not fully familiar with the content of this thread as I found at the time of writing this reply.
In case I find a way to solve the issue in my project, I will post here what helped me solve the issue. As for now, I’m going to follow this thread.