Fix doclava arguments

We need to send the javacompile files AFTER they are resolved which
happens lazily. This lambda magic makes it lazy (given by Xav).

Bug: N/A
Test: builds fine.
Change-Id: Ie59e49456e84c50e2eacdd7a339475be8d6d565c

diff_and_docs.gradle

@@ -438,7 +438,7 @@ void registerForDocsTask(Task task, Project subProject, releaseVariant) {
                 fileTree(releaseVariant.aidlCompile.sourceOutputDir) +
                 fileTree(releaseVariant.outputs[0].processResources.sourceOutputDir)
     }
-    task.classpath += files(releaseVariant.javaCompile.classpath) +
+    task.classpath += files{releaseVariant.javaCompile.classpath.files} +
             files(releaseVariant.javaCompile.destinationDir)
 }