message: Update Spack ref
diff: "package_final_phase" : "hostconfig",
  "package_source_dir" : "../..",
  "spack_url": "https://github.com/spack/spack.git",
  -"spack_commit": "c2af154cd24ab3ef501a7efc020f818ef60aa552",
  +"spack_branch": "v0.18.1",
  "spack_activate" : {},
  "spack_configs_path": "tpl/RAJA/scripts/radiuss-spack-configs",
  "spack_packages_path": "scripts/spack_packages",
  