fix bench workflow (#101)

.github/workflows/bench.yml

@@ -23,9 +23,15 @@ jobs:
           key: ${{ runner.os }}-check-${{ hashFiles('**/Cargo.lock') }}
       - name: compare perf
         run: |
+          git fetch origin main
+          cd ..
           git clone https://github.com/higherorderco/hvm-compare-perf
           cd hvm-compare-perf
-          NO_COLOR=1 cargo run bench -r main -r ${{ github.sha }} -m intr-singl -m intr-multi > ../table
+          NO_COLOR=1 cargo run bench \
+            --core ../hvm-core \
+            -r main -r ${{ github.sha }} \
+            -m intr-singl -m intr-multi \
+            > ../hvm-core/table
       - name: write comment
         run: |
           echo 'Perf run for [`'`git rev-parse --short ${{ github.sha }}`'`](https://github.com/higherorderco/hvm-core/commit/${{ github.sha }}):' >> comment