We have *.class files for a good reason: they include gettext translations. If you absolutely require to kill that, you need to add "mvn -Ptranslate compile" step to perform "gettext" step. However, that would void "built from the same git source" statement.
That is somewhat risky, since the new jar is not usable for old JRE. In other words, if a software exists that uses Java 5 and jdbc2.jar, then newly build jar is not compatible with it.
In order to build jre7, and jre6-compatible jars, separate build steps should be used. We have https://github.com/pgjdbc/pgjdbc-jre7 & jre6 for that. Vladimir