Export PRODUCT_COPY_FILES to Soong

PRODUCT_COPY_FILES entries are used to auto generate the prebuilt_*
modules in filesystem_creator.

Test: m nothing
Bug: 375053752
Change-Id: I7ed49645d9ab11f6b57f257b5741a855ac86c688
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 01e4697..a511d5c 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -426,6 +426,11 @@
   $(call add_json_list, ProductPackages, $(PRODUCT_PACKAGES))
   $(call add_json_list, ProductPackagesDebug, $(PRODUCT_PACKAGES_DEBUG))
 
+  $(call add_json_map, ProductCopyFiles)
+  $(foreach pair,$(PRODUCT_COPY_FILES),\
+    $(call add_json_str,$(word 1,$(subst :, ,$(pair))),$(word 2,$(subst :, ,$(pair)))))
+  $(call end_json_map)
+
 $(call end_json_map)
 
 $(call json_end)