- this layout is a pain to work with
- without a common root, it's painful to express things like "disable clangd" (D61122)
- CMake/lit configs are a maintenance hazard, and the more the one-off hacks for various tools are entangled, the more we see apathy and non-ownership.
This attempts to use the bare-minimum configuration needed (while still
supporting the difficult cases: windows, standalone clang build, dynamic libs).
In particular the lit.cfg.py and lit.site.cfg.py.in are merged into lit.cfg.in.
The logic in these files is now minimal.
(Much of clang-tools-extra's lit configs can probably be cleaned up by reusing
lit.llvm.llvm_config.use_clang(), and every llvm project does its own version of
LDPATH mangling. I haven't attempted to fix any of those).
Docs are still in clang-tools-extra/docs, I don't have any plans to touch those.