DO NOT COMMIT: testing fetch/unpack times of no-checkout custom image

Author: gburgessiv

.github/workflows/premerge.yaml

@@ -29,7 +29,9 @@ jobs:
     if: >-
         github.repository_owner == 'llvm' &&
         (github.event_name != 'pull_request' || github.event.action != 'closed')
-    runs-on: llvm-premerge-linux-runners
+    runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/gburgessiv/llvm-ci-with-checkout:no-checkout
     steps:
       - name: Seed LLVM repo
         run: |