Merge #3345

3345: Try adding button to clear cabal cache in buildkite r=Anviking a=Anviking

- [x] Try adding button to clear cabal cache in buildkite
    - When not pressing the button...
        - [x] The build should pass (iff previous steps pass)
        - [x] The cache should not be cleared
    - When pressing the button...
        - [x] The cache should be cleared
        - [x] Even if previous steps fail 

### Comments

- Pressing the button will unfortunately only clear the cache on one of the containers 😕 

### Issue Number

None

<!-- Reference the Jira/GitHub issue that this PR relates to, and which requirements it tackles.
  Note: Jira issues of the form ADP- will be auto-linked. -->


Co-authored-by: Johannes Lund <johannes.lund@iohk.io>

.buildkite/pipeline.yml

@@ -91,3 +91,13 @@ steps:
       - './scripts/shellcheck.sh'
     agents:
       system: x86_64-linux
+
+  - block: "Clear cabal cache"
+    key: 'should_clear_cache'
+    allow_dependency_failure: true
+    depends_on: [] # allows triggering this step even if previous steps failed
+
+  - label: 'Clearing cabal cache'
+    command: 'rm -vrf $CABAL_DIR'
+    agents:
+      system: x86_64-linux