CI: Build Rust code reference

.gitlab-ci.yml

@@ -94,6 +94,22 @@ build_deb:future:
     - debuild -i -us -uc -b
     - cp ../*.deb .
 
+build_reference:
+  stage: build
+  needs:
+    - job: build_meson
+      artifacts: true
+  artifacts:
+    paths:
+      - _build/doc
+  script:
+    - apt-get -y install cargo
+    - cd _build
+    - ../cargo.sh doc --no-deps --document-private-items
+  except:
+    variables:
+      - $PKG_ONLY == "1"
+
 test_lintian:
   stage: test
   needs: