add bins directory before running download

.github/workflows/build.yaml

@@ -27,6 +27,8 @@ jobs:
         python -m pip install --upgrade pip
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Download bins
-      run: python download_bins.py
+      run: |
+        mkdir -p bins
+        python download_bins.py
     - name: Try building
       run: python main.py