java: add genrule support to java builds

Add support for source files generated by genrule or gensrcs to
java builds.

Change-Id: I39762b2ab65fa4cf92724300edc4ba995845ce92
diff --git a/Blueprints b/Blueprints
index 3953dbf..6f3c487 100644
--- a/Blueprints
+++ b/Blueprints
@@ -141,6 +141,7 @@
         "blueprint",
         "blueprint-pathtools",
         "soong-common",
+        "soong-genrule",
     ],
     srcs: [
         "java/app_builder.go",