Enable blacksmith global artifact caching

Author: apiraino

build.bash

@@ -1,9 +1,6 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-CARGO_TARGET_DIR=${CARGO_TARGET_DIR:-"$PWD"/target}
-export CARGO_TARGET_DIR
-
 if [ "${RUN_BLACKSMITH:-0}" = "1" ]; then
   cargo run --locked --manifest-path=blacksmith/Cargo.toml -- "$@"
 else