Bug#789802: lintian: False positive source-contains-prebuilt-java-object reported against jar files without classes

[Emmanuel Bourg <ebourg@apache.org>]

maven-invoker-plugin is a good example of a package containing
empty jar files. The source tarball ships with 3 jar files used
by the integration tests, they contain only a MANIFEST.MF file
and no compiled class:

ebourg@icare:~/packaging/maven-invoker-plugin$ tar -tf ../maven-invoker-plugin_1.5.orig.tar.gz | grep jar
maven-invoker-plugin-1.5/src/it/staging-dependencies/repo/org/apache/maven/its/minvoker-70/1.0-SNAPSHOT/minvoker-70-1.0-20081020.164906-1.jar
maven-invoker-plugin-1.5/src/it/staging-dependencies/repo/org/apache/maven/its/dep/1.0/dep-1.0-tests.jar
maven-invoker-plugin-1.5/src/it/staging-dependencies/repo/org/apache/maven/its/dep/2.0/dep-2.0.jar

ebourg@icare:~/packaging/maven-invoker-plugin$ jar -tf src/it/staging-dependencies/repo/org/apache/maven/its/dep/1.0/dep-1.0-tests.jar
META-INF/
META-INF/MANIFEST.MF