Export BoardUsesGenericKernelImage to Soong

Test: m nothing
Bug: 379190521
Change-Id: Iab59acfe5db056afe652922826381b4821440c4d
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 7c07010..c247c21 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -439,6 +439,7 @@
   $(call add_json_str, BoardInitBootimagePartitionSize, $(BOARD_INIT_BOOTIMAGE_PARTITION_SIZE))
   $(call add_json_str, BoardBootHeaderVersion, $(BOARD_BOOT_HEADER_VERSION))
   $(call add_json_str, TargetKernelPath, $(TARGET_KERNEL_PATH))
+  $(call add_json_bool, BoardUsesGenericKernelImage, $(BOARD_USES_GENERIC_KERNEL_IMAGE))
 
   # Avb (android verified boot) stuff
   $(call add_json_bool, BoardAvbEnable, $(filter true,$(BOARD_AVB_ENABLE)))