upd for prev commit
now script is using compiler from "$project.retrolambda.jdk/bin/java"

If system's default JDK isn't 1.8 than retrolambda had problems.

Java task was completely unaware of *retrolambda.jdk* option and adndroid on only used library from JDK8, but if compiler was from JDK7 it failed output 1.8 class files.

Now both compile task and retrolambda tasks are running using JDK8 in separate process, if we have different JDK running gradle.