Function build_wasm_canisters_cached 

pub fn build_wasm_canisters_cached(
    spec: &WasmBuildSpec,
) -> Result<WasmBuildOutcome, WasmBuildError>

Build or reuse one exact set of Cargo Wasm artifacts.

The operation takes an exclusive process lock scoped to target_dir, then fingerprints all declared inputs. A cache hit requires both a matching atomic stamp and every expected nonempty Wasm output. Failed or interrupted builds never publish a successful stamp.