Move rootfs.raw.img to cache

- Seems odd that the cached rootfs ends up in out, leading to un-needed
copying (or potentially rebuilding) every time one cleans. Move it out
to the cache folder with debootstraps.

Change-Id: I07075e45fc6a5742180b3bee95464c5ae1778b50
diff --git a/rootfs.mk b/rootfs.mk
index 3aee89a..2c7d1a1 100644
--- a/rootfs.mk
+++ b/rootfs.mk
@@ -5,7 +5,7 @@
 include $(ROOTDIR)/build/preamble.mk
 
 ROOTFS_DIR := $(PRODUCT_OUT)/obj/ROOTFS/rootfs
-ROOTFS_RAW_IMG := $(PRODUCT_OUT)/obj/ROOTFS/rootfs.raw.img
+ROOTFS_RAW_IMG := $(ROOTDIR)/cache/rootfs.raw.img
 ROOTFS_PATCHED_IMG := $(PRODUCT_OUT)/obj/ROOTFS/rootfs.patched.img
 
 ROOTFS_FETCH_TARBALL ?= true
@@ -91,8 +91,8 @@
                        | $(PRODUCT_OUT)/boot.img \
                          modules \
                          packages
-	cp -r $(ROOTFS_RAW_IMG) $(ROOTFS_PATCHED_IMG)
 	mkdir -p $(ROOTFS_DIR)
+	cp -r $(ROOTFS_RAW_IMG) $(ROOTFS_PATCHED_IMG)
 	-sudo umount $(ROOTFS_DIR)/boot
 	-sudo umount $(ROOTFS_DIR)
 	sudo mount -o loop $(ROOTFS_PATCHED_IMG) $(ROOTFS_DIR)