chore(gitlab-ci): add backend dependencies setup with (more) proper caching

.gitlab-ci.yml

@@ -58,6 +58,23 @@ node modules:
   retry: 2
   interruptible: true
 
+backend dependencies:
+  stage: setup
+  cache:
+    - &stack-cache
+      key: default-stack
+      paths:
+        - ${HOME}/.stack/
+        - .stack-work/
+  script:
+    - "nix shell .#gnumake .#stack .#coreutils --command make backend-dependencies"
+  before_script: *nix-before
+  artifacts:
+    paths:
+      - ${HOME}/.stack/
+  retry: 2
+  interruptible: true
+
 frontend lint:
   stage: lint
   script:
@@ -96,21 +113,21 @@ frontend build:
 
 backend lint:
   stage: lint
+  cache:
+    - *stack-cache
   script:
-    - "nix shell .#gnumake .#coreutils .#stack --command make CI=1 backend-lint"
+    - "nix shell .#gnumake .#stack --command make CI=1 backend-lint"
   before_script: *nix-before
+  needs:
+    - job: backend dependencies
+      artifacts: true
   retry: 2
   interruptible: true
 
 backend build:
   stage: build
   cache:
-    - &stack-cache
-      key: default-stack
-      paths:
-        - .stack/
-        - .stack-work/
-
+    - *stack-cache
   script:
     - "nix shell .#gnumake .#coreutils .#stack --command make CI=1 backend-build"
     - cp $(stack path --dist-dir)/build/hlint/hlint bin/test-hlint
@@ -119,6 +136,8 @@ backend build:
   needs:
     - job: node modules # transitive
       artifacts: false
+    - job: backend dependencies
+      artifacts: true
     - job: frontend lint # transitive
       artifacts: false
     - job: frontend build