Use same perf tests for benchcomp in CI (rust-lang#2429)

Co-authored-by: Zyad Hassan <[email protected]>

Author: qinheping

.github/workflows/kani.yml

@@ -303,6 +303,9 @@ jobs:
       - name: Build Kani (old variant)
         run: pushd old && cargo build-dev
 
+      - name: Copy benchmarks from new to old
+        run: rm -rf ./old/tests/perf ; cp -r ./new/tests/perf ./old/tests/
+
       - name: Run benchcomp
         run: |
           new/tools/benchcomp/bin/benchcomp \