Add support for combining the notices from 2 roots.

Apparently needed for cts tests due to apks putting intermediate files under
TARGET_OUT even when going to HOST_OUT.

Test: m with and without change verified no differences in notice files

Change-Id: Iea50b6bd9af9452a2600c97e2f7cb89218b9be7f
diff --git a/core/Makefile b/core/Makefile
index 584a144..8395e45 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -940,7 +940,7 @@
 	                $(if $(filter $(1),xml_vendor_dlkm),-i vendor_dlkm --xml-output, \
 	                  $(if $(filter $(1),xml_odm_dlkm),-i odm_dlkm --xml-output, \
 	                    --html-output)))))))) $(3) \
-	    -t $$(PRIVATE_MESSAGE) -s $$(PRIVATE_DIR)/src
+	    -t $$(PRIVATE_MESSAGE) $$(foreach dir,$$(sort $$(PRIVATE_DIR)), -s $$(dir)/src)
 notice_files: $(2) $(3)
 endef