build: fix build with CONFIG_STRIP_KERNEL_EXPORTS

Only use symtab.h on the final kernel link

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/kernel-defaults.mk

@@ -3,7 +3,7 @@
 # Copyright (C) 2006-2020 OpenWrt.org
 
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
-  KERNEL_MAKEOPTS += \
+  KERNEL_MAKEOPTS_IMAGE += \
 	EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"
 endif
 
@@ -137,7 +137,7 @@ endef
 
 define Kernel/CompileImage/Default
 	rm -f $(TARGET_DIR)/init
-	+$(KERNEL_MAKE) $(if $(KERNELNAME),$(KERNELNAME),all)
+	+$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all)
 	$(call Kernel/CopyImage)
 endef
 
@@ -147,7 +147,7 @@ define Kernel/CompileImage/Initramfs
 	$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(TARGET_DIR)/init
 	$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(TARGET_DIR)/init)
 	rm -rf $(KERNEL_BUILD_DIR)/linux-$(LINUX_VERSION)/usr/initramfs_data.cpio*
-	+$(KERNEL_MAKE) $(if $(KERNELNAME),$(KERNELNAME),all)
+	+$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all)
 	$(call Kernel/CopyImage,-initramfs)
 endef
 else