wasm-builder: Make `hash` and `date` optional (#14490)

* wasm-builder: Make `hash` and `date` optional

Apparently there are installations where the `hash` and `date` is optional.

Closes: https://github.com/paritytech/substrate/issues/14335

* ".git/.scripts/commands/fmt/fmt.sh"

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Co-authored-by: command-bot <>