use aapt to build jar files instead of the system zip (DO NOT MERGE)

By using 'aapt add' instead of whatever 'zip' utility happens to be
installed on the machine, we get files that are imgdiff-friendly,
which makes for smaller incremental OTAs.

(This is a cherry-pick of a change already submitted to eclair-mr2;
the change was approved for mr1.)

core/definitions.mk

@@ -1334,11 +1334,9 @@ $(hide) (cd $(dir $@) && zip -r $(notdir $@) lib)
 $(hide) rm -rf $(dir $@)lib
 endef
 
-#TODO: use aapt instead of zip, once it supports junking the path
-#      (so adding "xxx/yyy/classes.dex" appears as "classes.dex")
 #TODO: update the manifest to point to the dex file
 define add-dex-to-package
-$(hide) zip -qj $@ $(PRIVATE_DEX_FILE)
+$(hide) $(AAPT) add -k $@ $(PRIVATE_DEX_FILE)
 endef
 
 define add-java-resources-to-package