Add "TARGET_BOARD_PLATFORM" into soong_variables

Bug: 360872208
Bug: 348120216
Test: aosp_cf_x86_64_phone-trunk_staging-eng && m hosttar
Change-Id: Ie5f630818c5bd538265a969abbb50f1fbe255f91
diff --git a/core/soong_config.mk b/core/soong_config.mk
index f2e2283..14ea2aa 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -206,6 +206,7 @@
 $(call add_json_str,  BoardSepolicyVers,                 $(BOARD_SEPOLICY_VERS))
 $(call add_json_str,  SystemExtSepolicyPrebuiltApiDir,   $(BOARD_SYSTEM_EXT_PREBUILT_DIR))
 $(call add_json_str,  ProductSepolicyPrebuiltApiDir,     $(BOARD_PRODUCT_PREBUILT_DIR))
+$(call add_json_str,  BoardPlatform,                     $(TARGET_BOARD_PLATFORM))
 
 $(call add_json_str,  PlatformSepolicyVersion,           $(PLATFORM_SEPOLICY_VERSION))
 $(call add_json_list, PlatformSepolicyCompatVersions,    $(PLATFORM_SEPOLICY_COMPAT_VERSIONS))