Use rmdir /s/q instead of flaky shutil.rmtree on Windows

build/clobber.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """This script provides methods for clobbering build directories."""
 
 import argparse
 import os
 import shutil
+import subprocess
 import sys
 
 
 def extract_gn_build_commands(build_ninja_file):
   """Extracts from a build.ninja the commands to run GN.
 
   The commands to run GN are the gn rule and build.ninja build step at the
   top of the build.ninja file. We want to keep these when deleting GN builds
   since we want to preserve the command-line flags to GN.
 
   On error, returns the empty string."""
   result = ""
   with open(build_ninja_file, 'r') as f:
     # Read until the second blank line. The first thing GN writes to the file
     # is the "rule gn" and the second is the section for "build build.ninja",
     # separated by blank lines.
     num_blank_lines = 0
     while num_blank_lines < 2:
       line = f.readline()
       if len(line) == 0:
         return ''  # Unexpected EOF.
       result += line
       if line[0] == '\n':
         num_blank_lines = num_blank_lines + 1
   return result
 
 
+def delete_dir(build_dir):
+  # For unknown reasons (anti-virus?) rmtree of Chromium build directories
+  # often fails on Windows.
+  if sys.platform.startswith('win'):
+    subprocess.check_call(['rmdir', '/s', '/q', build_dir], shell=True)
+  else:
+    shutil.rmtree(build_dir)
+
+
 def delete_build_dir(build_dir):
   # GN writes a build.ninja.d file. Note that not all GN builds have args.gn.
   build_ninja_d_file = os.path.join(build_dir, 'build.ninja.d')
   if not os.path.exists(build_ninja_d_file):
-    shutil.rmtree(build_dir)
+    delete_dir(build_dir)
     return
 
   # GN builds aren't automatically regenerated when you sync. To avoid
   # messing with the GN workflow, erase everything but the args file, and
   # write a dummy build.ninja file that will automatically rerun GN the next
   # time Ninja is run.
   build_ninja_file = os.path.join(build_dir, 'build.ninja')
   build_commands = extract_gn_build_commands(build_ninja_file)
 
   try:
     gn_args_file = os.path.join(build_dir, 'args.gn')
     with open(gn_args_file, 'r') as f:
       args_contents = f.read()
   except IOError:
     args_contents = ''
 
-  shutil.rmtree(build_dir)
+  delete_dir(build_dir)
 
   # Put back the args file (if any).
   os.mkdir(build_dir)
   if args_contents != '':
     with open(gn_args_file, 'w') as f:
       f.write(args_contents)
 
   # Write the build.ninja file sufficiently to regenerate itself.
   with open(os.path.join(build_dir, 'build.ninja'), 'w') as f:
     if build_commands != '':
@@ skipping 31 matching lines @@
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('out_dir', help='The output directory to clobber')
   args = parser.parse_args()
   clobber(args.out_dir)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())