Make landmines.py take an extra script via an env var.

build/landmines.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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 runs every build as a hook. If it detects that the build should
 be clobbered, it will touch the file <build_dir>/.landmine_triggered. The
 various build scripts will then check for the presence of this file and clobber
 accordingly. The script will also emit the reasons for the clobber to stdout.
@@ skipping 65 matching lines @@
           fromfile='old_landmines', tofile='new_landmines',
           fromfiledate=old_date, tofiledate=time.ctime(), n=0)
 
       with open(triggered, 'w') as f:
         f.writelines(diff)
     elif os.path.exists(triggered):
       # Remove false triggered landmines.
       os.remove(triggered)
 
 
-def main():
+def process_options():
+  """Returns a list of landmine emitting scripts."""
   parser = optparse.OptionParser()
   parser.add_option(
       '-s', '--landmine-scripts', action='append',
       default=[os.path.join(SRC_DIR, 'build', 'get_landmines.py')],
       help='Path to the script which emits landmines to stdout. The target '
-           'is passed to this script via option -t.')
+           'is passed to this script via option -t. Note that an extra '
+           'script can be specified via an env var EXTRA_LANDMINES_SCRIPT.')
   parser.add_option('-v', '--verbose', action='store_true',
       default=('LANDMINES_VERBOSE' in os.environ),
       help=('Emit some extra debugging information (default off). This option '
           'is also enabled by the presence of a LANDMINES_VERBOSE environment '
           'variable.'))
 
   options, args = parser.parse_args()
 
   if args:
     parser.error('Unknown arguments %s' % args)
 
   logging.basicConfig(
       level=logging.DEBUG if options.verbose else logging.ERROR)
 
+  extra_script = os.environ.get('EXTRA_LANDMINES_SCRIPT')
+  if extra_script:
+    return options.landmine_scripts + [extra_script]
+  else:
+    return options.landmine_scripts
+
+
+def main():
+  landmine_scripts = process_options()
   gyp_helper.apply_chromium_gyp_env()
 
   for target in ('Debug', 'Release', 'Debug_x64', 'Release_x64'):
     landmines = []
-    for s in options.landmine_scripts:
+    for s in landmine_scripts:
       proc = subprocess.Popen([sys.executable, s, '-t', target],
                               stdout=subprocess.PIPE)
       output, _ = proc.communicate()
       landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
     set_up_landmines(target, landmines)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())