Add generation of dependency file for .ap_ package

Make Aapt generate a dependency file in the same directory as the
output ap_ file if the --generate-dependencies flag is set.
This dependency file can then be read by the ant exec loop task
to see whether to repackage resources.

Change-Id: I763679414daf76369700aa599c26dcf78d4de099
diff --git a/tools/aapt/Main.cpp b/tools/aapt/Main.cpp
index 8edb5b5..9887268 100644
--- a/tools/aapt/Main.cpp
+++ b/tools/aapt/Main.cpp
@@ -148,7 +148,7 @@
         "   --extra-packages\n"
         "       generate R.java for libraries. Separate libraries with ':'.\n"
         "   --generate-dependencies\n"
-        "       generate a dependency file for R.java.\n"
+        "       generate dependency files in the same directories for R.java and resource package\n"
         "   --auto-add-overlay\n"
         "       Automatically add resources that are only in overlays.\n"
         "   --rename-manifest-package\n"