Remove unavailable features As we use Debian packaged libzstd not the bundled, some features are not (can not be) enabled at build time and unavailable, or made no-op: - debug, fat-lto, no_asm, thin, thin-lto: only useful with bundled zstd - zstdmt: deprecated, upstream hidden by default - legacy: Debian package has it on - pkg-config: always used - std: no-op with use-std-c-ffi.patch
