kernel-defaults: ensure SOURCE_DATE_EPOCH on /init

This is a follow up of 8cb13f4e6d which sets the right timestamp for the
/init file in initramfs. The previous patch doesn't cover it as the
files appear to come from a later step during compilation.

CC: Alexander Couzens <lynxis@fe80.eu>

Signed-off-by: Paul Spooren <mail@aparcar.org>

include/kernel-defaults.mk

@@ -146,6 +146,7 @@ ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
 define Kernel/CompileImage/Initramfs
 	$(call Kernel/Configure/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) modules
 	$(call Kernel/CopyImage,-initramfs)