[clang] [lldb] [llvm] [cmake] Add support for statically linking libxml2 (PR #166867)

[Keith Smiley via llvm-commits]

keith wrote:

i also submitted an upstream PR so that hopefully we can do this without as much copy-pasta in the future https://gitlab.kitware.com/cmake/cmake/-/merge_requests/11476

https://github.com/llvm/llvm-project/pull/166867