Use latest Bazel version

Author: fwouts

.circleci/config.yml

@@ -12,7 +12,7 @@ install_bazel: &install_bazel
  name: Install Bazel
  command: |
  sudo apt-get install pkg-config zip g++ zlib1g-dev unzip python
- BAZEL_VERSION=0.17.2
+ BAZEL_VERSION=0.21.0
  BAZEL_INSTALL_SCRIPT=bazel-$BAZEL_VERSION-installer-linux-x86_64.sh
  wget https://github.com/bazelbuild/bazel/releases/download/$BAZEL_VERSION/$BAZEL_INSTALL_SCRIPT
  chmod +x $BAZEL_INSTALL_SCRIPT