This is how I managed to build TensorFlow 2.0 on Ubuntu 18.04 (x86_64) with Bazelisk:
$ sudo apt update
$ sudo apt full-upgrade
$ sudo apt install curl
# Install Bazelisk.
$ sudo curl -Lo /usr/local/bin/bazel https://github.com/bazelbuild/bazelisk/releases/download/v1.1.0/bazelisk-linux-amd64
$ sudo chmod +x /usr/local/bin/bazel