community/olm: upgrade to 3.2.12
https://gitlab.matrix.org/matrix-org/olm/-/tags/3.2.12
This release includes the following changes since 3.2.11:
- Expose
olm_sas_calculate_mac_fixed_base64
in the bindings.- Allow memory to grow in wasm. Thanks to benkuly for the suggestion.
- Fix Python type hints.
- Some Python build fixes.
- Initial work on a Nix flake for building and testing.