Create clear_cache.yml

Add a manual action to delete caches creating by GitHub actions. The usual maximum size allowed for all caches is 10GB, which we can easily fill with a PR having a good number of commits. When the 10GB is full, workflows will start failing.

.github/workflows/clear_cache.yml

@@ -0,0 +1,30 @@
+name: Clear cache
+
+on:
+  workflow_dispatch:
+
+permissions:
+  actions: write
+
+jobs:
+  clear-cache:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clear cache
+        uses: actions/github-script@v6
+        with:
+          script: |
+            console.log("About to clear")
+            const caches = await github.rest.actions.getActionsCacheList({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+            })
+            for (const cache of caches.data.actions_caches) {
+              console.log(cache)
+              github.rest.actions.deleteActionsCacheById({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                cache_id: cache.id,
+              })
+            }
+            console.log("Clear completed")