benchs: use the guix env also for database.sh script

.gitlab-ci.yml

@@ -107,7 +107,9 @@ database:
   #extends: .only-main-mr
   needs: ['benchmark']
   script:
-    - ./scripts/database.sh
+    - guix time-machine -C .guix/scalfmm-channels.scm -- shell --pure --preserve="^CI|proxy$"
+        -m .guix/scalfmm-manifest-gcc-mkl-bench.scm
+        -- /bin/bash --norc ./scripts/database.sh
   artifacts:
     when: always
     paths: