make: add clean cmd

Author: Horki

Makefile

@@ -69,4 +69,7 @@ install-timing:
 	cargo install --features=timing --path "." --offline
 
 licenses:
-	cargo bundle-licenses --format toml --output THIRDPARTY.toml
+	cargo bundle-licenses --format toml --output THIRDPARTY.toml
+
+clean:
+	cargo clean