While this is essentially what we now do in Jenkins using its "Copy Workspace" functionality, it may not be necessary in Evergreen since it's easy in a single task to use Java 8 to compile production and test classes, and then any other version of Java to run the tests with something like:

gradlew -Porg.gradle.java.home=/opt/java/java6 -x classes -x testClasses --rerun-tasks test 

or

export JAVA_HOME=/opt/java/java6
gradlew -x classes -x testClasses --rerun-tasks test 

Compilation itself takes less than 30 seconds so there's not a whole lot of savings to be had by re-using the artifacts.

We would need it, however, to test on any platform without a Java 8 JDK available.