To build the latest version just follow this steps
(NB: Subversion's client and Maven2 should be installed on your system)
$ svn export http://dev.lutece.paris.fr/svn/lutece/portal/trunk/plugins/plugin-googleapi plugin-googleapi
$ cd plugin-googleapi
$ mvn lutece:assembly
The last command will build the plugin's package as an archive named plugin-googleapi-xxx-bin-xxxx.zip in the directory ./target/assembly
To deploy this package, just extract its content in your webapp's root.
As soon as the plugin has been extracted in the webapp, just activate it in the "Plugins management" feature of the Lutece backoffice
In the file WEB-INF/conf/plugins/googleapi.properties set your API key and default project id as follows :
# Your Google API key. googleapi.api.key=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx