Flink ML 2.1.0 Installation

Trying to go through Flink-ML quickstart but having an issue with building Flink ML's source code.

Steps to reproduce:

1. sudo wget https://dlcdn.apache.org/flink/flink-ml-2.1.0/flink-ml-2.1.0-src.tgz
2. sudo tar -xzf flink-ml-2.1.0-src.tgz
3. mvn clean package -DskipTests -Dcheckstyle.skip

Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:2.17:check (validate) on project flink-ml-parent: Unable to create output stream: /usr/src/flink-ml-2.1.0/target/checkstyle-result.xml: /usr/src/flink-ml-2.1.0/target/checkstyle-result.xml (No such file or directory) -> [Help 1]

It doesn't seem like `target` is a folder in `flink-ml-2.1.0`.