Add ramdisk.img to the dist dir, again (was removed at some point) - from master - please do no merge
b/2590492 and requested again

Change-Id: I1f4efac2a8ca47f1b69761bb9233427e0ca0411d
diff --git a/core/main.mk b/core/main.mk
index 2f6b297..b79e2ea 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -718,6 +718,7 @@
     $(INSTALLED_BUILD_PROP_TARGET) \
     $(BUILT_TARGET_FILES_PACKAGE) \
     $(INSTALLED_ANDROID_INFO_TXT_TARGET) \
+    $(INSTALLED_RAMDISK_TARGET) \
    )
 
   # Tests are installed in userdata.img.  If we're building the tests