Fix benchmark job

.circleci/config.yml

@@ -125,6 +125,7 @@ jobs:
       - run:
           name: dependencies
           command: |
+            sudo bash -c "echo \"deb http://ftp.us.debian.org/debian testing main contrib non-free\" >> /etc/apt/sources.list"
             sudo apt-get update
             sudo apt-get install -t testing g++-8
             sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 60 --slave /usr/bin/g++ g++ /usr/bin/g++-6