Add PRODUCT_PACKAGES to soong.variables

Bug: 297269187
Test: m bazel_sandwich
Change-Id: Iea8877b7fe56f7cd0e5e227ce0e6597bdc708162

core/soong_config.mk

diff --git a/core/soong_config.mk b/core/soong_config.mk
index f68c741..58d3d6f 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -381,6 +381,8 @@
   $(call add_json_bool, CopyImagesForTargetFilesZip, $(filter true,$(COPY_IMAGES_FOR_TARGET_FILES_ZIP)))
 
   $(call add_json_bool, BoardAvbEnable, $(filter true,$(BOARD_AVB_ENABLE)))
+
+  $(call add_json_list, ProductPackages, $(sort $(PRODUCT_PACKAGES)))
 $(call end_json_map)
 
 $(call add_json_bool, NextReleaseHideFlaggedApi, $(filter true,$(PRODUCT_NEXT_RELEASE_HIDE_FLAGGED_API)))