build: move definition of KBUILD_BUILD_TIMESTAMP to include/kernel.mk

Fixes: 0aed054bec (build: add KERNEL_MAKE and KERNEL_MAKE_FLAGS
variables and move to kernel.mk)

Signed-off-by: Alexander Couzens <lynxis@fe80.eu>

include/kernel-defaults.mk

@@ -5,12 +5,6 @@
 # See /LICENSE for more information.
 #
 
-ifneq ($(SOURCE_DATE_EPOCH),)
-  ifndef DUMP
-    KBUILD_BUILD_TIMESTAMP:=$(shell perl -e 'print scalar gmtime($(SOURCE_DATE_EPOCH))')
-  endif
-endif
-
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
   KERNEL_MAKEOPTS += \
 	EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"

include/kernel.mk

@@ -10,6 +10,12 @@ CHECK:=1
 DUMP:=1
 endif
 
+ifneq ($(SOURCE_DATE_EPOCH),)
+  ifndef DUMP
+    KBUILD_BUILD_TIMESTAMP:=$(shell perl -e 'print scalar gmtime($(SOURCE_DATE_EPOCH))')
+  endif
+endif
+
 ifeq ($(__target_inc),)
   ifndef CHECK
     include $(INCLUDE_DIR)/target.mk