Make sure maven is installed correctly.
Use mvn clean install
in the root directory.
To revert back to default build location.
Open pom.xml
and locate
<build>
...
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<outputDirectory>./Server/start.bat</outputDirectory>
</configuration>
</plugin>
</plugins>
</build>
Delete the plugin to use mavens default build path.
Please do not commit changes to the pom.xml unless they are needed. For example don't commit the changing of the outputDirectory.