Export BOARD_SYSTEM_KERNEL_MODULES related variables to soong

This will be used to generate the deps of the autogenerated soong
system_dlkm.img

Test: presubmits
Bug: 376726109
Change-Id: Ida0b47aa7db39fd789151ee3ed7029e36d8e6247
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 988b5c1..02dacd8 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -432,6 +432,10 @@
   $(call add_json_list, VendorLinkerConfigSrcs, $(PRODUCT_VENDOR_LINKER_CONFIG_FRAGMENTS))
   $(call add_json_list, ProductLinkerConfigSrcs, $(PRODUCT_PRODUCT_LINKER_CONFIG_FRAGMENTS))
 
+  # Used to generate _dlkm partitions
+  $(call add_json_bool, BuildingSystemDlkmImage,               $(BUILDING_SYSTEM_DLKM_IMAGE))
+  $(call add_json_list, SystemKernelModules, $(BOARD_SYSTEM_KERNEL_MODULES))
+
   $(call add_json_map, ProductCopyFiles)
   $(foreach pair,$(PRODUCT_COPY_FILES),\
     $(call add_json_str,$(word 1,$(subst :, ,$(pair))),$(word 2,$(subst :, ,$(pair)))))