release workflow: Add build scripts for jobs and means to upload pkgs

bin/rebuild-index.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+set -x
+
+SPACK_BIN_DIR="${CI_PROJECT_DIR}/bin"
+export PATH="${SPACK_BIN_DIR}:${PATH}"
+
+spack upload-s3 index