One issue to keep in mind regarding the dependencies, is that while most of them only are needed at build time, the Python dependency does end up as a runtime dependency for the built LLDB; if unavailable, LLDB doesn’t launch at all. So whatever version of Python is chosen and used for that, it needs to be fairly straightforward for users to install the corresponding version.
(Or ideally, maybe that version of Python could be bundled in the releases? In llvm-mingw, we bundle a small, stripped down build of Python in the release packages - that way, LLDB is fully featured and doesn’t rely on users finding a matching version of a third party package.)