Compatibility with JDK9 requires an update of plexus-archiver

The Maven Jar plugin will fail when running on Java 9 since preview build 95 (since inclusion of project Verona) because of a small issue in the used version of plexus-archiver.

See also:

• https://github.com/codehaus-plexus/plexus-archiver/issues/13

The trivial fix was merged:

• https://github.com/codehaus-plexus/plexus-archiver/pull/12

This is to track the need for an update to a `plexus-archiver` version including the above patches. Would love to see a Maven release including this too, so that we can use our project's existing testsuites to test for Java9 compatibility ASAP.