Docker: Add error message for missing spack cache

tools/docker/scripts/setup_spack_cache.sh

@@ -0,0 +1,23 @@
+#!/bin/bash -e
+
+# author: Ole Schuett
+
+if [[ -n "${SPACK_CACHE}" ]]; then
+  if [[ "${SPACK_CACHE}" == *"http://localhost:9000"* ]]; then
+    if ! wget -q --tries=1 "http://localhost:9000/spack-cache"; then
+      echo ""
+      echo "ERROR: Could not connect to local Spack cache."
+      echo "       Start the cache by running ./start_spack_cache.sh and then pass --network=host to podman."
+      echo "       Alternatively, disable the cache by passing --build-arg SPACK_CACHE=\"\" to podman."
+      echo "       See also: https://manual.cp2k.org/trunk/getting-started/build-with-spack.html"
+      echo ""
+      exit 1
+    fi
+  fi
+  echo "Adding Spack cache: ${SPACK_CACHE}"
+  spack mirror add --autopush --unsigned local-cache "${SPACK_CACHE}"
+else
+  echo "No Spack cache provided."
+fi
+
+#EOF