Add makefile_goal.

Only for boot images.

Test: add one makefile_goal
Bug: 158537840
Change-Id: I88a006a1c7bfbf79f10f5360aae27a9bc267e42d
diff --git a/android/Android.bp b/android/Android.bp
index 487372b..c196b7a 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -23,6 +23,7 @@
         "filegroup.go",
         "hooks.go",
         "image.go",
+        "makefile_goal.go",
         "makevars.go",
         "metrics.go",
         "module.go",