These files are from the llvm-project based on release 22.1.8.
We maintain a local fork of llvm-project that contains any Emscripten specific patches:
https://github.com/emscripten-core/llvm-project
The current patch is based on the emscripten-libs-22 branch.
Run system/lib/update_libcxxabi.py path/to/llvm-project
For a list of changes from upstream see the libcxxabi files that are part of:
https://github.com/llvm/llvm-project/compare/llvmorg-22.1.8...emscripten-core:emscripten-libs-22