fix(CI): find correct upstream prefix when it's padded

install_spack_env.sh

@@ -48,10 +48,11 @@ fi
 
 if [[ $UPSTREAM_INSTANCE ]]
 then
+  UPSTREAM_PREFIX=$(find $UPSTREAM_INSTANCE/spack/opt/spack/ -type d -name ".spack-db" 2>/dev/null | xargs -I {} dirname {})
   cat <<EOF > ${CI_SPACK_ROOT}/etc/spack/defaults/upstreams.yaml
 upstreams:
   upstream-spack-instance:
-    install_tree: $UPSTREAM_INSTANCE/spack/opt/spack
+    install_tree: $UPSTREAM_PREFIX
 EOF
 fi