Pass COMMIT_DATE to the build

.gitlab-ci.yml

@@ -30,6 +30,7 @@ version_scheduled_job:
   before_script:
     - find "$CI_PROJECT_DIR" -path "$CI_PROJECT_DIR/.git" -prune -o "(" -type d -a -not -perm -u=w ")" -exec chmod --verbose u+w {} ";"
     - nix-env -f channel:nixos-unstable -iA gnutar gitMinimal
+    - export COMMIT_DATE="$(git show --no-patch --format=%ci)"
 
 # The binary produced is useless by itself
 binary: