Add AOT output dir to compile classpath

[mogenson]

Problem

ClojureCompileTask sets the Clojure compile output directory only via the clojure.compile.path system property (the destination for generated .class files). It is not added to the javaexec classpath.

Consequently, when a namespace (:import ...)s or directly constructs a gen-class'd class produced by a sibling namespace compiled earlier in the same task, the AOT compiler's DynamicClassLoader cannot resolve it — the sibling's .class file exists on disk but the output dir is not a classpath root. Compilation fails with:

Caused by: java.lang.ClassNotFoundException: com.example.MyGeneratedClass
  at clojure.lang.RT.classForName(RT.java:...)
  at com.example.my_service$loading__...invoke(my_service.clj:1)   ; the ns form

This is common for apps with multiple gen-class'd Android entry points — e.g. a WallpaperService that constructs its gen-class'd Engine, or a Worker referenced by name. (Discovered while porting a live-wallpaper app whose BingWallpaperService builds its BingEngine.)

Fix

Prepend destinationDir to the javaexec classpath. Classes generated by earlier-compiled namespaces are now on the classpath, so a later namespace can :import / construct them directly. This removes the need to resolve such classes reflectively via Class/forName.

Test

Ported com.binglivewallpaper.wallpaper-service from a reflective Class/forName lookup to a direct (BingEngine. this) constructor call. With this change, compileDebugClojure succeeds (it previously threw ClassNotFoundException: com.binglivewallpaper.BingEngine), all three gen-class'd entry-point classes are emitted, the full assembleDebug APK builds, and the unit tests pass.