Only include deb files and Packages in packages.tgz

- Previously, we included the entire contents of $PRODUCT_OUT/packages
in the tarball that we deploy to the rootfs. Change this to only include
.deb files and the Packages file, which contains the repository
metadata.
- Saves several hundred megabytes on the rootfs of a development build
on Excelsior.

Change-Id: I14a01e168e1b6e00892df6dc29e635337f318722
diff --git a/packages.mk b/packages.mk
index 2ad9107..4ff2c86 100644
--- a/packages.mk
+++ b/packages.mk
@@ -153,7 +153,9 @@
 packages-tarball: $(ROOTDIR)/cache/packages.tgz
 $(ROOTDIR)/cache/packages.tgz: $(ALL_PACKAGE_TARGETS) | out-dirs
 	$(ROOTDIR)/build/update_packages.sh
-	tar -C $(PRODUCT_OUT) --overwrite -czf $@ packages
+	find $(PRODUCT_OUT)/packages -name '*.deb' -or -name 'Packages' | \
+		sed -e "s#$(PRODUCT_OUT)/##g" | \
+		tar -C $(PRODUCT_OUT) --overwrite -czf $@ -T -
 
 $(PRODUCT_OUT)/mendel.list: $(ROOTDIR)/build/mendel.list.template
 	sed -e "s;%BOARDNAME%;$(BOARD_NAME);g" $(ROOTDIR)/build/mendel.list.template > $(PRODUCT_OUT)/mendel.list