Make sure directory exists, of course

Author: NattyNarwhal

.github/workflows/ci.yml

@@ -47,6 +47,7 @@ jobs:
         if: steps.cache-docker.outputs.cache-hit != 'true'
         run: |
           docker pull ibmcom/db2
+          mkdir image-cache
           docker save -o image-cache/db2.tar ibmcom/db2
       - name: Restore container from cache
         if: steps.cache-docker.outputs.cache-hit == 'true'