community/py3-zstandard: use bundled zstd
The build uses headers and internals from the bundled zstd, and it does not work well when linking to a system lib with different version.
This fixes the following error:
ImportError: zstd C API versions mismatch; Python bindings were not
compiled/linked against expected zstd version (10506 returned by the
lib, 10506 hardcoded in zstd headers, 10505 hardcoded in the cext)