Export PLATFORM_VERSION_KNOWN_CODENAMES to soong

Bug: 236602028
Test: watch TH
Change-Id: Ieb156dfb363e58ef4949cf5a340b3011f310097f
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 7b8f6df..9b5cd1e 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -34,6 +34,7 @@
 $(call add_json_str,  Platform_preview_sdk_version,      $(PLATFORM_PREVIEW_SDK_VERSION))
 $(call add_json_str,  Platform_base_os,                  $(PLATFORM_BASE_OS))
 $(call add_json_str,  Platform_version_last_stable,      $(PLATFORM_VERSION_LAST_STABLE))
+$(call add_json_str,  Platform_version_known_codenames,  $(PLATFORM_VERSION_KNOWN_CODENAMES))
 
 $(call add_json_str,  Platform_min_supported_target_sdk_version, $(PLATFORM_MIN_SUPPORTED_TARGET_SDK_VERSION))