Use depfile for desugar.py

This patch makes following command do nothing in second run.
$ ninja -C out/android_n5x_swarming_rel/ chrome_sync_shell_apk

Bug: 646165
Change-Id: If95d3691bffdfbdba2fbbc0b71f01af2c08214fc
Reviewed-on: https://chromium-review.googlesource.com/923466Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@google.com>
Cr-Commit-Position: refs/heads/master@{#537748}

build/config/android/internal_rules.gni

@@ -1289,6 +1289,8 @@ if (enable_java_templates) {
         }
         inputs += [ _android_sdk_ijar ]
         args = [
+          "--depfile",
+          rebase_path(depfile, root_build_dir),
           "--input-jar",
           rebase_path(_desugar_input_jar, root_build_dir),
           "--output-jar",