core: allow product to provide kernel headers as well

This is useful when a device inherits from an architecture
product, such as omap4.mk. The architecture specific product
can provide kernel headers to all the devices that use
that architecture.

Change-Id: I0c9d3120a6089fb535a3fa8eccf10775a271cd21
Signed-off-by: Dima Zavin <dima@android.com>
diff --git a/core/product.mk b/core/product.mk
index 23dc375..b001ca2 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -86,6 +86,7 @@
     PRODUCT_DEFAULT_DEV_CERTIFICATE \
     PRODUCT_RESTRICT_VENDOR_FILES \
     PRODUCT_FACTORY_RAMDISK_MODULES \
+    PRODUCT_VENDOR_KERNEL_HEADERS \
 
 
 define dump-product
@@ -201,6 +202,9 @@
 	TARGET_ARCH_VARIANT \
 	TARGET_BOARD_PLATFORM \
 	TARGET_BOARD_PLATFORM_GPU \
+	TARGET_BOARD_KERNEL_HEADERS \
+	TARGET_DEVICE_KERNEL_HEADERS \
+	TARGET_PRODUCT_KERNEL_HEADERS \
 	TARGET_BOOTLOADER_BOARD_NAME \
 	TARGET_COMPRESS_MODULE_SYMBOLS \
 	TARGET_NO_BOOTLOADER \