supersize: Fix --toolprefix="" not being followed

tools/binary_size/libsupersize/paths.py

 # Copyright 2017 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.
 
 """Functions for dealing with determining --tool-prefix."""
 
 import distutils.spawn
 import logging
 import os
 
 _STATUS_DETECTED = 1
 _STATUS_VERIFIED = 2
 
 
 class LazyPaths(object):
   def __init__(self, tool_prefix=None, output_directory=None,
                any_path_within_output_directory=None):
     self._tool_prefix = tool_prefix
     self._output_directory = output_directory
     self._any_path_within_output_directory = any_path_within_output_directory
-    self._output_directory_status = _STATUS_DETECTED if output_directory else 0
-    self._tool_prefix_status = _STATUS_DETECTED if tool_prefix else 0
+    self._output_directory_status = (
+        _STATUS_DETECTED if output_directory is not None else 0)
+    self._tool_prefix_status = (
+        _STATUS_DETECTED if tool_prefix is not None else 0)
 
   @property
   def tool_prefix(self):
     if self._tool_prefix_status < _STATUS_DETECTED:
       self._tool_prefix_status = _STATUS_DETECTED
       self._tool_prefix = self._DetectToolPrefix() or ''
       logging.debug('Detected --tool-prefix=%s', self._tool_prefix)
     return self._tool_prefix
 
   @property
@@ skipping 48 matching lines @@
     output_directory = self.output_directory
     if output_directory:
       # Auto-detect from build_vars.txt
       build_vars_path = os.path.join(output_directory, 'build_vars.txt')
       if os.path.exists(build_vars_path):
         with open(build_vars_path) as f:
           build_vars = dict(l.rstrip().split('=', 1) for l in f if '=' in l)
         return os.path.normpath(
             os.path.join(output_directory, build_vars['android_tool_prefix']))
     return None