Add DropPrivileges()

util/util.gyp

 # Copyright 2014 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 66 matching lines @@
         'net/http_headers.h',
         'net/http_multipart_builder.cc',
         'net/http_multipart_builder.h',
         'net/http_transport.cc',
         'net/http_transport.h',
         'net/http_transport_mac.mm',
         'numeric/checked_range.h',
         'numeric/in_range_cast.h',
         'numeric/int128.h',
         'numeric/safe_assignment.h',
+        'posix/drop_privileges.cc',
+        'posix/drop_privileges.h',
         'posix/process_info.h',
         'posix/process_info_mac.cc',
         'posix/symbolic_constants_posix.cc',
         'posix/symbolic_constants_posix.h',
         'stdlib/cxx.h',
         'stdlib/objc.h',
         'stdlib/pointer_container.h',
         'stdlib/string_number_conversion.cc',
         'stdlib/string_number_conversion.h',
         'stdlib/strlcpy.cc',
@@ skipping 157 matching lines @@
     },
     {
       'target_name': 'util_test_multiprocess_exec_test_child',
       'type': 'executable',
       'sources': [
         'test/multiprocess_exec_test_child.cc',
       ],
     },
   ],
 }