Fix a subtle proguard incremental build error

build/android/gyp/proguard.py

 #!/usr/bin/env python
 #
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import optparse
 import os
 import sys
 
@@ skipping 48 matching lines @@
 
   options.input_paths = build_utils.ParseGnList(options.input_paths)
 
   return options
 
 
 def main(args):
   args = build_utils.ExpandFileArgs(args)
   options = _ParseOptions(args)
 
+  # Work around cases where we switch from a non-proguard setup
+  # to proguard. The output jar might exist and might be a hardlink
+  # to the input jar, so remove the output before doing anything
+  # in that case to avoid an incremental build failure.
+  try:
+    out_inode = os.stat(options.output_path).st_ino
+  except OSError:
+    out_inode = None
+  if (out_inode and
+      out_inode in (os.stat(injar).st_ino for injar in options.input_paths)):
+    os.unlink(options.output_path)
+
   proguard = proguard_util.ProguardCmdBuilder(options.proguard_path)
   proguard.injars(options.input_paths)
   proguard.configs(options.proguard_configs)
   proguard.outjar(options.output_path)
 
   if options.mapping:
     proguard.mapping(options.mapping)
 
   if options.tested_apk_info:
     proguard.tested_apk_info(options.tested_apk_info)
 
   classpath = list(set(options.classpath))
   proguard.libraryjars(classpath)
   proguard.verbose(options.verbose)
   if not options.enable_dangerous_optimizations:
     proguard.disable_optimizations(_DANGEROUS_OPTIMIZATIONS)
 
   input_paths = proguard.GetInputs()
 
   build_utils.CallAndWriteDepfileIfStale(
       proguard.CheckOutput,
       options,
       input_paths=input_paths,
       input_strings=proguard.build(),
       output_paths=[options.output_path])
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))