List hashes and use them

.gitlab-ci.yml

@@ -141,10 +141,12 @@ spack:install_compilers:
       --show-log-on-error
       ${COMPILER_LIST_SPECS}
 
+    - hashes=$(jq -r '.spec.nodes | map("/\(.hash)") | join(" ")' compilers_spec.json)
+
     - spack/bin/spack buildcache create
       --update-index
       --key EDC904DCE3D2E84E
-      /buildcache $( jq -r '.spec.nodes | map("/\(.hash)") | join(" ")' compilers_spec.json )
+      /buildcache ${hashes}
 
     - |
       echo 'definitions: [ compilers: [' ${COMPILER_LIST_SPECS} ']]' > compiler_definitions.yaml