Function build_compound 

pub fn build_compound(
    xid: u32,
    tag: &str,
    uid: u32,
    gid: u32,
    machine: &str,
    ops: &[Nfs4Op],
) -> Vec<u8> 

Build an NFSv4.2 COMPOUND RPC call body (XDR, no record mark).

Returns the XDR-encoded RPC body ready for frame_rpc_message or super::client::NfsCompoundClient::rpc_call.