libxml2 is required for building on Windows since LLVM 14

Identified in #922.

* @apmasell Suggested that it may be required for emitted remarks: https://github.com/numba/llvmlite/pull/922#issuecomment-1476061341
* On Linux and macOS, we explicitly disable it: https://github.com/numba/llvmlite/blob/main/conda-recipes/llvmdev/build_llvm14.sh#L31

We should determine whether it's really needed and disable it if not.

Start with conda-recipes/llvmdev/build_llvm14.sh and compare its explicit libxml2 handling with the Windows build behavior described in #922. Determine whether emitted remarks require libxml2; done means confirming the dependency is necessary or disabling it for Windows when it is not.

Written by the indexing model from the issue text.