Android: use gcc (not cpp) to preprocess templates.

build/android/java_cpp_template.gypi

 # 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 file is meant to be included into a target to provide a rule
 # to generate Java source files from templates that are processed
 # through the host C pre-processor.
 #
-# This assumes a GNU-compatible pre-processor installed as 'cpp'.
-# Only tested on Linux.
-#
 # To use this, create a gyp target with the following form:
 #  {
 #    'target_name': 'android_net_java_constants',
 #    'type': 'none',
 #    'sources': [
 #      'net/android/NetError.template',
 #    ],
 #    'variables': {
 #      'package_name': 'org/chromium/net',
 #      'template_deps': ['net/base/certificate_mime_type_list.h'],
@@ skipping 28 matching lines @@
   'rules': [
     {
       'rule_name': 'generate_java_constants',
       'extension': 'template',
       # Set template_deps as additional dependencies.
       'inputs': ['<@(template_deps)'],
       'outputs': [
         '<(output_dir)/<(RULE_INPUT_ROOT).java'
       ],
       'action': [
-        'cpp',                 # invoke host pre-processor.
+        'gcc',                 # invoke host gcc.
+        '-E',                  # stop after preprocessing.
         '-x', 'c-header',      # treat sources as C header files
         '-P',                  # disable line markers, i.e. '#line 309'
         '-I', '<(DEPTH)',      # Add project top-level to include path
         '-o', '<@(_outputs)',  # Specify output file
         '<(RULE_INPUT_PATH)',  # Specify input file
       ],
       'message': 'Generating Java from cpp template <(RULE_INPUT_PATH)',
     }
   ],
 }