do not prefix with artifacts if absolute path given

[dzmitry-lahoda]

 nix run .#beaker -- wasm  store-code ./result/lib/cw_xc_gateway  --signer-mnemonic "$CI_COSMOS_MNEMONIC"

expands to

artifacts./result/lib/cw_xc_gateway

expected

<Dir with Beaker.toml>/result/lib/cw_xc_gateway