Fix unit testing in modules needing engine-tests + natives

[Cervator]

Example module is Pathfinding, which had a transitive dependency on engine-tests (before I changed Core's build.gradle to blindly always depend on latest engine + engine-tests, probably temporarily) as well as a need for natives

While Jenkins now copies in natives for module builds unit tests that depend on an origin class in engine-tests, such as HeadlessEnvironment, the execution starts within the Gradle cache directory which is where the engine-tests jar ends up. Then natives detection fails to find the natives directory in the job workspace

http://jenkins.movingblocks.net/view/Modules/job/Pathfinding/106/console
MovingBlocks@a3181c1