[llvm] [llvm] Fix incorrect usage of `LIBXML2_INCLUDE_DIRS` in the Windows release script (PR #95781)

[Carlos Alberto Enciso via llvm-commits]

CarlosAlbertoEnciso wrote:

Looking at those original changes:

> cmake -GNinja %cmake_flags% -DPYTHON_HOME=%python64_dir% -DPython3_ROOT_DIR=%python64_dir% -DLIBXML2_INCLUDE_DIR=%libxmldir%/include/libxml2 -DLIBXML2_LIBRARIES=%libxmldir%/lib/libxml2s.lib ..\llvm-project\llvm || exit /b

It is clear that the `LIBXML2_INCLUDE_DIR` is being set to the `%libxmldir%/include/libxml2`, which is what the patch is setting.

https://github.com/llvm/llvm-project/pull/95781