Enable wasmtime caching for PVF (companion for #8057) (#2387)

* Wasm caching

* Fix compilation errors

* Rename `cache_path` to `cache_base_path`

* "Update Substrate"

* Fix check-web-wasm build

Co-authored-by: parity-processbot <>

polkadot/cli/src/cli.rs

@@ -60,6 +60,9 @@ pub enum Subcommand {
 #[allow(missing_docs)]
 #[derive(Debug, StructOpt)]
 pub struct ValidationWorkerCommand {
+	/// The path that the executor can use for it's caching purposes.
+	pub cache_base_path: Option<std::path::PathBuf>,
+
 	#[allow(missing_docs)]
 	pub mem_id: String,
 }