Add depfile support to android build scripts

build/config/android/internal_rules.gni

Index: build/config/android/internal_rules.gni
diff --git a/build/config/android/internal_rules.gni b/build/config/android/internal_rules.gni
index b3114ef1690eaca6741f1c6081e770afde35c647..a85fe996e52129bd22aa6b16a7610a4ec986874e 100644
--- a/build/config/android/internal_rules.gni
+++ b/build/config/android/internal_rules.gni
@@ -9,9 +9,11 @@ template("zip") {
   rebase_output = rebase_path(invoker.output)
   action(target_name) {
     script = "//build/android/gn/zip.py"
+    depfile = "$target_gen_dir/$target_name.d"
     source_prereqs = invoker.inputs
-    outputs = [invoker.output]
+    outputs = [depfile, invoker.output]

[cjhopman, 2014/06/23 15:08:21]

afaict, ninja expects the depfile to specify the dependencies for the first
output :/. I would really prefer to just be able to write a list of paths that
ninja would add to the inputs.

Also, is it possible that ninja doesn't treat the depfile as an input to the
action? I expect that if it did, it couldn't also be specified as an output. If
it isn't treated as an input, that is rather unexpected.

     args = [
+      "--depfile", rebase_path(depfile, root_build_dir),
       "--inputs=$rebase_inputs",
       "--output=$rebase_output",
     ]