Fix RRO when LOCAL_EXPORT_PACKAGE_RESOURCES is unset

If LOCAL_EXPORT_PACKAGE_RESOURCES is unset then
append_enforce_rro_sources was inserting a blank entry into
the 4th.  When converting the || separator back to space that
resulted in a two sequential spaces, which is treated as a
single word separator, causing the 5th field to be treated
as the 4th field.

Put "false" into the 4th field in soong_app_prebuilt.mk to match
package_internal.mk.

Bug: 123510624
Test: m SystemUIGoogle
Change-Id: I794c413e33df2020d0dc43379cfb017e7e09baa1
diff --git a/core/soong_app_prebuilt.mk b/core/soong_app_prebuilt.mk
index a6315b4..f8186c2 100644
--- a/core/soong_app_prebuilt.mk
+++ b/core/soong_app_prebuilt.mk
@@ -160,7 +160,7 @@
       $(my_register_name), \
       false, \
       $(LOCAL_FULL_MANIFEST_FILE), \
-      $(LOCAL_EXPORT_PACKAGE_RESOURCES), \
+      $(if $(LOCAL_EXPORT_PACKAGE_RESOURCES),true,false), \
       $(LOCAL_SOONG_RRO_DIRS))
 endif