message: chore: export build_tx. ckb-fake-env need this function, but it's private.
diff: @@ -6,6 +6,7 @@ mod verify;
  use ckb_vm::Error as VMInternalError;
  use serde_derive::{Deserialize, Serialize};
  +pub use crate::syscalls::build_tx;
  pub use crate::verify::TransactionScriptsVerifier;
  #[derive(Clone, Serialize, Deserialize, Eq, PartialEq, Hash, Debug)]
  