Export PRODUCT_VENDOR_LINKER_CONFIG_FRAGMENTS to soong

This will be used to create linker.config.pb file in the autogenerated
vendor `android_filesystem`.

Test: verified that linker.config.pb is present in the autogenerated
soong vendor.img
Bug: 375686533

Change-Id: I3f0ef6322fdfe28fb77c8599d1c8871d187b74a5
diff --git a/core/soong_config.mk b/core/soong_config.mk
index a5cbfc9..b608d2f 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -427,6 +427,9 @@
   $(call add_json_list, ProductPackages, $(PRODUCT_PACKAGES))
   $(call add_json_list, ProductPackagesDebug, $(PRODUCT_PACKAGES_DEBUG))
 
+  # Used to generate /vendor/linker.config.pb
+  $(call add_json_list, VendorLinkerConfigSrcs, $(PRODUCT_VENDOR_LINKER_CONFIG_FRAGMENTS))
+
   $(call add_json_map, ProductCopyFiles)
   $(foreach pair,$(PRODUCT_COPY_FILES),\
     $(call add_json_str,$(word 1,$(subst :, ,$(pair))),$(word 2,$(subst :, ,$(pair)))))