Add build.prop to factory ramdisk

We'll need a special case to set device properties on the factory ramdisk

Change-Id: I146d5c503e8c97005caa1ab1dbaca7ee9ab30faf
Signed-off-by: Nick Sanders <nsanders@google.com>
diff --git a/core/tasks/factory_ramdisk.mk b/core/tasks/factory_ramdisk.mk
index 6757194..2cbea87 100644
--- a/core/tasks/factory_ramdisk.mk
+++ b/core/tasks/factory_ramdisk.mk
@@ -60,6 +60,10 @@
 
 ifneq (,$(INTERNAL_FACTORY_RAMDISK_EXTRA_MODULES_FILES)$(INTERNAL_FACTORY_RAMDISK_FILES))
 
+# These files are made by magic in build/core/Makefile so we need to explicitly include them
+$(eval $(call copy-one-file,$(TARGET_OUT)/build.prop,$(TARGET_FACTORY_RAMDISK_OUT)/system/build.prop))
+INTERNAL_FACTORY_RAMDISK_FILES += $(TARGET_FACTORY_RAMDISK_OUT)/system/build.prop
+
 BUILT_FACTORY_RAMDISK_FS := $(PRODUCT_OUT)/factory_ramdisk.gz
 BUILT_FACTORY_RAMDISK_TARGET := $(PRODUCT_OUT)/factory_ramdisk.img