avoid doubled checkout

Signed-off-by: Dominik <[email protected]>

.github/workflows/build_and_test.yaml

@@ -55,22 +55,13 @@ jobs:
           restore-keys: |
             compile-${{ env.branch_name_for_cache }}-
             compile-
-      - name: Checkout from `everest-core` the `.ci/` directory (reusable workflow mode, see https://stackoverflow.com/a/74123003/1168315)
+      - name: Checkout `everest-core` (to only get the `.ci/` directory if reusable workflow mode, see https://stackoverflow.com/a/74123003/1168315)
         uses: actions/checkout@v4
         with:
-          sparse-checkout: |
-            .ci
           repository: EVerest/everest-core
           ref: CI/reusable-workflow  # TODO get reference in general, see https://stackoverflow.com/questions/74784735 resp. https://github.com/actions/toolkit/issues/1264
-      - name: Move `.ci/` to `/tmp` and remove `everest-core`
-        run: |
-          mv .ci /tmp
-          pwd && ls -hal .
-          cd ..
-          pwd && ls -hal .
-          rm -rf everest-core
-          pwd && ls -hal .
-      - name: Checkout repo ${{ inputs.repository || 'EVerest/everest-core' }}
+      - name: Checkout repo ${{ inputs.repository }}
+        if: ${{ github.repository != EVerest/everest-core }}
         uses: actions/checkout@v4
         with:
           repository: ${{ inputs.repository }}